Compact accessory systems for a gas turbine engine

ABSTRACT

An accessory system for a gas turbine engine having a driveshaft is provided. The accessory system includes a towershaft coupled to the driveshaft and driven by the driveshaft. The accessory system also includes a shaft including a first shaft bevel gear coupled to a towershaft bevel gear. The shaft is rotatable by the towershaft. The accessory system includes a first accessory drive shaft having a first accessory bevel gear driven by the shaft. The accessory system also includes a second accessory drive shaft having a second accessory bevel gear driven by the shaft.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/057,507 filed on Aug. 7, 2018, which is a divisional of U.S. patentapplication Ser. No. 15/014,097 filed on Feb. 3, 2016 and issued as U.S.Pat. No. 10,662,878. The relevant disclosure of each of the aboveapplications is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to gas turbine engines, andmore particularly relates to compact accessory systems for a gas turbineengine, such as a compact accessory gearbox for use with a gas turbineengine.

BACKGROUND

Gas turbine engines may be employed to power various devices. Forexample, a gas turbine engine may be employed to power a mobileplatform, such as an aircraft. Typically, gas turbine engines includeaccessories that assist in engine operation and in the operation of themobile platform, which are driven by the gas turbine engine. Theaccessories are generally positioned within an engine nacelle. Thearrangement of the accessories in the engine nacelle influences the sizeof the engine nacelle, which may increase drag on the mobile platform.

Accordingly, it is desirable to provide compact accessory systems for agas turbine engine, which includes a compact accessory gearbox having areduced size that enables a reduction in a volume of an engine nacelle.Furthermore, other desirable features and characteristics of the presentinvention will become apparent from the subsequent detailed descriptionand the appended claims, taken in conjunction with the accompanyingdrawings and the foregoing technical field and background.

SUMMARY

In various embodiments, provided is an accessory system for a gasturbine engine having a driveshaft with an axis of rotation. Theaccessory system includes a towershaft coupled to the driveshaft anddriven by the driveshaft along a towershaft axis of rotation transverseto the axis of rotation of the gas turbine engine. The towershaftincludes a towershaft bevel gear at a distal end. The accessory systemalso includes a shaft including a first shaft bevel gear coupled to thetowershaft bevel gear. The shaft is rotatable by the towershaft along ashaft axis of rotation. The shaft axis of rotation is transverse to thetowershaft axis of rotation and substantially parallel to the axis ofrotation of the gas turbine engine. The accessory system includes afirst accessory drive shaft having a first accessory bevel gear drivenby the shaft, and the first accessory drive shaft has a first accessoryaxis of rotation. The accessory system also includes a second accessorydrive shaft having a second accessory bevel gear driven by the shaft.The second accessory drive shaft has a second accessory axis ofrotation, and each of the first accessory axis of rotation and thesecond accessory axis of rotation are substantially transverse to theshaft axis of rotation. The secondary accessory axis of rotation and thefirst accessory axis of rotation are substantially transverse to eachother.

Also provided according to various embodiment is an accessory system fora gas turbine engine having a driveshaft with an axis of rotation. Theaccessory system includes a towershaft coupled to the driveshaft anddriven by the driveshaft along a towershaft axis of rotation transverseto the axis of rotation of the gas turbine engine. The towershaftincludes a towershaft bevel gear at a distal end. The accessory systemcomprises a shaft including a first shaft bevel gear coupled to thetowershaft bevel gear, and the shaft is rotatable by the towershaftalong a shaft axis of rotation. The shaft axis of rotation is transverseto the towershaft axis of rotation and substantially parallel to theaxis of rotation of the gas turbine engine. The shaft includes a secondshaft bevel gear spaced apart from a third shaft bevel gear by a spacer.The accessory system also includes a first accessory drive shaft havinga first accessory bevel gear coupled to the second shaft bevel gear, andthe first accessory drive shaft has a first accessory axis of rotation.The accessory system includes a second accessory drive shaft having asecond accessory bevel gear coupled to the third shaft bevel gear. Thesecond accessory drive shaft has a second accessory axis of rotation,and each of the first accessory axis of rotation and the secondaccessory axis of rotation are substantially transverse to the shaftaxis of rotation. The secondary accessory axis of rotation and the firstaccessory axis of rotation are substantially transverse to each other.

Further provided according to various embodiments is an accessory systemfor a gas turbine engine having a driveshaft with an axis of rotation.The accessory system includes a towershaft coupled to the driveshaft anddriven by the driveshaft along a towershaft axis of rotation transverseto the axis of rotation of the gas turbine engine. The towershaftincludes a towershaft bevel gear at a distal end. The accessory systemincludes a shaft including a first shaft bevel gear coupled to thetowershaft bevel gear. The shaft is rotatable by the towershaft along ashaft axis of rotation, and the shaft axis of rotation is transverse tothe towershaft axis of rotation and substantially parallel to the axisof rotation of the gas turbine engine. The accessory system alsoincludes a first accessory drive shaft having a first accessory bevelgear driven by the shaft, and the first accessory drive shaft has afirst accessory axis of rotation. The accessory system includes a secondaccessory drive shaft having a second accessory bevel gear driven by theshaft. The second accessory drive shaft has a second accessory axis ofrotation, and each of the first accessory axis of rotation and thesecond accessory axis of rotation are substantially transverse to theshaft axis of rotation. The secondary accessory axis of rotation and thefirst accessory axis of rotation are substantially transverse to eachother, and the first accessory axis of rotation intersects the shaftaxis of rotation at a first point and the second accessory axis ofrotation intersects the shaft axis of rotation at a second point. Theaccessory system includes a third accessory drive shaft having a thirdaccessory bevel gear driven by the shaft. The third accessory driveshaft has a third accessory axis of rotation, and the third accessoryaxis of rotation intersects the shaft axis of rotation at a third point,with the second point different than the first point and the thirdpoint.

DESCRIPTION OF THE DRAWINGS

The exemplary embodiments will hereinafter be described in conjunctionwith the following drawing figures, wherein like numerals denote likeelements, and wherein:

FIG. 1 is a schematic cross-sectional illustration of a gas turbineengine, which includes an exemplary compact accessory system includingan exemplary compact accessory gearbox in accordance with the variousteachings of the present disclosure;

FIG. 1B is a schematic cross-sectional illustration of a gas turbineengine, which includes an exemplary compact accessory system includingan exemplary compact accessory gearbox in accordance with the variousteachings of the present disclosure;

FIG. 2 is a top view of the compact accessory system of FIG. 1;

FIG. 3 is a bottom view of the compact accessory system of FIG. 1, witha portion of the compact accessory gearbox removed;

FIG. 4 is a front view of an exemplary adaptor for use with the compactaccessory system of FIG. 1;

FIG. 5 is a cross-sectional view of the adaptor of FIG. 4, taken alongline 5-5 of FIG. 4;

FIG. 6 is an exploded perspective view of an exemplary bearing assemblyfor use with the compact accessory system of FIG. 1;

FIG. 7 is an exploded perspective view of the adaptor of FIG. 4;

FIG. 8 is a top view of the compact accessory gearbox of FIG. 1;

FIG. 9 is a back view of the compact accessory gearbox of FIG. 1;

FIG. 10 is a bottom view of a gear train of the compact accessorygearbox of FIG. 1;

FIG. 10A is a schematic perspective illustration of the gear train ofFIG. 10, which illustrates that a portion of the gear train is on animaginary cone;

FIG. 10B is a schematic perspective illustration of the gear train ofFIG. 10, which illustrates that a portion of the gear train is on animaginary cone;

FIG. 11 is an exploded perspective view of a shaft for use with the geartrain of FIG. 10 and the compact accessory gearbox of FIG. 1;

FIG. 12 is a cross-sectional view of the compact accessory gearbox ofFIG. 8, taken along line 12-12 of FIG. 8;

FIG. 13 is a perspective view of an exemplary oil tank for use with thecompact accessory gearbox of FIG. 1;

FIG. 14 is a schematic bottom view of a compact accessory gearbox foruse with the compact accessory system of FIG. 1 according to the variousteachings of the present disclosure;

FIG. 15 is a top view of a compact accessory system for use with the gasturbine engine of FIG. 1, which includes a compact accessory gearbox inaccordance with the various teachings of the present disclosure;

FIG. 16 is a top view of a gear train for use with the compact accessorygearbox of FIG. 15;

FIG. 17 is a cross-sectional view of the gear train of FIG. 16, takenalong line 17-17 of FIG. 16;

FIG. 18 is a top view of a gear train for use with the compact accessorygearbox of FIG. 15 in accordance with the various teachings of thepresent disclosure; and

FIG. 19 is a cross-sectional view of the gear train of FIG. 18, takenalong line 19-19 of FIG. 18.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the application and uses. Furthermore, there is nointention to be bound by any expressed or implied theory presented inthe preceding technical field, background, brief summary or thefollowing detailed description. In addition, those skilled in the artwill appreciate that embodiments of the present disclosure may bepracticed in conjunction with any type of gearbox that would benefitfrom a reduced or compact configuration, and that the accessory systemsand methods described herein for use with a gas turbine engine is merelyone exemplary embodiment according to the present disclosure. Moreover,while the accessory systems and methods are described herein as beingused with a gas turbine engine onboard a mobile platform, such as a bus,motorcycle, train, motor vehicle, marine vessel, aircraft, rotorcraftand the like, the various teachings of the present disclosure can beused with a gas turbine engine on a stationary platform. Further, itshould be noted that many alternative or additional functionalrelationships or physical connections may be present in an embodiment ofthe present disclosure. In addition, while the figures shown hereindepict an example with certain arrangements of elements, additionalintervening elements, devices, features, or components may be present inan actual embodiment. It should also be understood that the drawings aremerely illustrative and may not be drawn to scale.

With reference to FIG. 1, a cross-sectional view of an exemplary gasturbine engine 10 is shown, which includes a compact accessory system 12according to various embodiments. It should be noted that while thecompact accessory system 12 is discussed herein with regard to the gasturbine engine 10, the compact accessory system 12 can be employed withany suitable engine, such as a turbojet engine, an auxiliary power unit(APU), etc. Thus, the following description is merely one exemplary useof the compact accessory system 12. Moreover, while the gas turbineengine 10 is described herein as being used with a mobile platform, suchas an aircraft 8, it will be understood that the gas turbine engine 10may be used with any suitable platform, whether mobile or stationary.

In this example, the gas turbine engine 10 includes a fan section 14, acompressor section 16, a combustor section 18, a turbine section 20, andan exhaust section 22. The fan section 14 includes a fan 24 mounted on arotor 26 that draws air into the gas turbine engine 10 and acceleratesit. A fraction of the accelerated air exhausted from the fan 24 isdirected through an outer (or first) bypass duct 28 and the remainingfraction of air exhausted from the fan 24 is directed into thecompressor 32.

In the embodiment of FIG. 1, the compressor section 16 includes acompressor 32. However, in other embodiments, the number of compressorsin the compressor section 16 may vary. In the depicted embodiment, thecompressor 32 raises the pressure of the air and directs the highpressure air into the combustor 36. A fraction of the air bypasses thecombustor 36 and enters a second bypass duct 34.

In the embodiment of FIG. 1, in the combustor section 18, which includesan annular combustor 36, the high pressure air is mixed with fuel andcombusted. The high-temperature combusted air is then directed into theturbine section 20. The turbine section 20 includes three turbinesdisposed in axial flow series, namely, a high pressure turbine 38 and alow pressure turbine 42. However, it will be appreciated that the numberof turbines, and/or the configurations thereof, may vary. In thisembodiment, the high-temperature combusted air from the combustorsection 18 expands through and rotates each turbine 38 and 42. The airis then exhausted through a propulsion nozzle 44 disposed in the exhaustsection 22. As the turbines 38 and 42 rotate, each drives equipment inthe gas turbine engine 10 via concentrically disposed shafts or spools.In one example, the high pressure turbine 38 drives the compressor 32via a high pressure driveshaft 46 and the low pressure turbine 42 drivesthe fan 24 via a low pressure driveshaft 50. Generally, the highpressure driveshaft 46 and the low pressure driveshaft 50 are coaxiallyarranged along a longitudinal axis L of the gas turbine engine 10, andeach of the high pressure driveshaft 46 and the low pressure driveshaft50 have an axis of rotation R, which extends substantially parallel toand along the longitudinal axis L.

In the example of FIG. 1, the high pressure driveshaft 46 includes agear 52. In this example, the gear 52 is a bevel gear, having aplurality of bevel gear teeth. The gear 52 is coupled to a towershaft 54and drives the towershaft 54. In one example, the towershaft 54 includesa first end 54 a and a second end 54 b. The first end 54 a includes agear 56, which in this example, comprises a bevel gear. The gear 56includes a plurality of bevel gear teeth, which are meshingly coupled toor engaged with the plurality of bevel gear teeth of the gear 52. Theengagement of gear 56 with gear 52 transfers torque from the highpressure driveshaft 46 to the towershaft 54, and thus, drives or rotatesthe towershaft 54. The towershaft 54 is generally coupled to the gear 52such that the towershaft 54 extends along an axis of rotation Tr, whichis substantially transverse to the axis of rotation R of the highpressure driveshaft 46. One or more bearings or supports may be coupledto the towershaft 54 at or near the first end 54 a to support thetowershaft 54 for rotation with the gear 56.

The second end 54 b of the towershaft 54 is coupled to the compactaccessory system 12 and forms part of the compact accessory system 12.In one example, the second end 54 b of the towershaft 54 includes asleeve 55. The sleeve 55 is coupled about the second end 54 b viasplined coupling, for example, although any suitable joining techniquemay be employed such that the sleeve 55 rotates in unison with thetowershaft 54. The sleeve 55 may be supported for rotation by a bearing57, which is disposed in a housing 59. The housing 59 couples the secondend 55 b of the sleeve 55 to the compact accessory gearbox 60 and thebearing 57 supports the sleeve 55 for rotation relative to a compactaccessory gearbox 60. The sleeve 55 further includes a gear 58, such asa bevel gear. The gear 58 is disposed at a second end 55 b of the sleeve55, and includes a plurality of bevel gear teeth 58 a. The plurality ofbevel gear teeth 58 a are coupled about a perimeter or circumference ofthe gear 58. The gear 58 is coupled to the compact accessory system 12,and the plurality of bevel gear teeth 58 a meshingly engage a bevel gearcontained within the compact accessory gearbox 60 as will be discussedfurther herein. Generally, the gear 58 transfers torque from the sleeve55 and the towershaft 54 to the compact accessory gearbox 60 to drivevarious components of the compact accessory system 12. However, duringan engine startup, power is delivered from a starter turbine 64 (withair supplied by a starter valve 62) and into compact accessory gearbox60 at the correct speed (in revolutions per minute (rpm)), driving thesleeve 55 and the towershaft 54, which drives the high pressuredriveshaft 46 and turns the compressor 32 and high pressure turbine 38of the gas turbine engine 10 allowing the gas turbine engine 10 tostart. The compact accessory system 12, in turn, drives variousaccessories associated with the gas turbine engine 10. In one example,the compact accessory system 12 is mounted within a nacelle N of the gasturbine engine 10.

With reference to FIG. 2, the compact accessory system 12 is shown ingreater detail. In this example, the compact accessory system 12includes the compact accessory gearbox 60, which drives variousaccessories, including, but not limited to, a starter turbine 64, adirect-current (DC) generator 66, a hydraulic pump 68, a permanentmagnet alternator 70, a fuel control unit 72, a lubrication pump 74 andan air-oil separator 76 (FIG. 3). The starter valve 62 supplies air tothe starter turbine 64. Generally, the compact accessory gearbox 60 iscoupled to the towershaft 54 via the gear 58 to receive the torque fromthe towershaft 54 and to drive the accessories 62-76. It should be notedthat the accessories 62-76 described herein are merely exemplary, as thecompact accessory gearbox 60 may be used to drive any suitable accessoryassociated with the gas turbine engine 10. With brief reference to FIGS.4-6, the accessories 64-74 can be coupled to the compact accessorygearbox 60 via an adaptor 80.

With reference to FIGS. 4 and 5, the adaptor 80 includes an accessoryinterface 82 and a gearbox interface 84 (FIG. 5), which areinterconnected via a central bore 85. The adaptor 80 is composed of anysuitable material, and in one example, is composed of a metal or metalalloy. The adaptor 80 may be formed via casting, stamping, machining,etc. The accessory interface 82 is generally opposite the gearboxinterface 84 (FIG. 5). The accessory interface 82 is generally circular,however, the accessory interface 82 may have any desired shape to couplethe respective accessory 64-74 to the compact accessory gearbox 60.

In one example, the accessory interface 82 includes a first plurality ofmounting bores 86. The first plurality of mounting bores 86 are spacedapart along a perimeter or circumference of the accessory interface 82.In one example, the mounting bores 86 comprise mounting slots, which areelongated about the circumference of the accessory interface 82. In thisexample, two mounting fasteners (not shown) may be received in each ofthe mounting bores 86, with one of the mounting fasteners received in afirst end 86 a of the mounting bore 86, and another of the mountingfasteners received in a second end 86 b of the mounting bore 86. Whilenot illustrated herein for clarity, the mounting fasteners comprise anysuitable coupling device for coupling the accessory 62-74 to the adaptor80, including, but not limited to, a mechanical fastener assemblyincluding a threaded shank that engages a nut disposed about a surface86 c of the mounting bores 86, etc. In addition, one of the mountingbores 86′ may have a arcuate length about the perimeter of the accessoryinterface 82 that is different than a arcuate length of a reminder ofthe mounting bores 86″. In this example, the arcuate length of themounting bore 86′ is less than the arcuate length of the mounting bores86″ to aid in the alignment of the respective accessory 64-72 to theadaptor 80. Generally, with reference to FIG. 5, the mounting bores 86extend through an outer surface of the accessory interface 82 andterminate at a base 88 of the accessory interface 82. A v-band flange 88a may also be coupled to the adaptor 80, which may engage acorresponding v-band flange associated with one or more of theaccessories 64-72. The v-band flange 88 a allows the accessory 64-72with the corresponding or opposing v-band flange to be connected to theadaptor 80 using a v-band clamp.

In addition, with reference to FIG. 4, the accessory interface 82 mayinclude a piloting bore 87. The piloting bore 87 may receive a pilotingscrew or other device to assist in locating the respective accessory64-72 on the accessory interface 82. The piloting bore 87 generallyterminates at the base 88, as illustrated in FIG. 6. With continuedreference to FIG. 6, the accessory interface 82 also includes aprojection 89, which adds material for a breather port defined throughthe adaptor 80. The projection 89 is coupled to the base 88 of theaccessory interface 82, so as to be on a side of the base 88substantially opposite the mounting bores 86.

With reference to FIGS. 5 and 6, the gearbox interface 84 couples thecompact accessory gearbox 60 to the adaptor 80. The gearbox interface 84is generally circular, and has a diameter, which is different than adiameter of the accessory interface 82. The diameter of the gearboxinterface 84 is generally smaller than the accessory interface 82. Thegearbox interface 84 includes a second plurality of mounting bores 90,which pass through the gearbox interface 84 and terminate along asurface 91 a of a counterbore 91 defined through the accessory interface82. The mounting bores 90 are generally cylindrical, but the mountingbores 90 may have any desired shape. The mounting bores 90 are generallyspaced apart about a perimeter or circumference of the gearbox interface84. In one example, one of the mounting bores 90′ is spaced a greaterdistance apart from a reminder of the plurality of mounting bores 90″ toaid in the assembly, clocking and coupling of the adaptor 80 to thecompact accessory gearbox 60; however, the mounting bores 90 may beevenly spaced. In this example, the gearbox interface 84 defines threemounting bores 90; however, the gearbox interface 84 may include anynumber of mounting bores 90. The mounting bores 90 each receive asuitable mechanical fastener, such as a bolt, etc., which tightensagainst a nut or nutplate received on the surface 92 a, for example, tocouple the adaptor 80 to the compact accessory gearbox 60.

With reference to FIG. 5, the central bore 85 is defined about a centralaxis CL of the adaptor 80. In this example, the central bore 85 is sizedto receive a bearing assembly 93, which includes a first bearing 92, aspacer 94, a second bearing 96 and a retaining ring 98. The central bore85 includes a lip 100 at a first end 85 a, which serves to retain thefirst bearing 92 within the central bore 85. The central bore 85 alsodefines a recess 102 at a second end 85 b, which receives the retainingring 98 to retain the bearing assembly 93 within the central bore 85.Generally, the bearing assembly 93 enables a respective shaft of thecompact accessory gearbox 60 to rotate within the adaptor 80 to drivethe respective accessory 64-72. The first bearing 92 and the secondbearing 96 each generally comprise a ball bearing, roller bearing,duplex, air, or any other type of bearing, as known to one of skill inthe art. The spacer 94 comprises any suitable spacer, and in oneexample, comprises a metal ring that is received between the firstbearing 92 and the second bearing 96. The retaining ring 98 comprises ametal retaining ring, which is elastically deformable to enable theretaining ring 98 to be removably coupled to the central bore 85.

With reference to FIG. 6, a piloting flange 108 c is coaxial with thecentral bore 85 to assist in aligning the bearing assembly 93 within thecentral bore 85 and with a plurality of apertures 128 of a housing orgear case 120 of the compact accessory gearbox 60. In one example, agasket 104 includes a plurality of mounting bores 104 a that coaxiallyalign with the plurality of mounting bores 90 to enable the mechanicalfastening assembly associated with the gearbox interface 84 to passthrough the mounting bores 104 a and couple a flange 108 b with thegasket 104 and the gearbox interface 84. The piloting flange 108 c alsodefines a central bore 104 b, which is sized to be positioned about thecentral bore 85.

With reference back to FIGS. 2 and 3, as the accessories 62-74 aregenerally known to one skilled in the art, the accessories 62-74 willnot be discussed in great detail herein. Briefly, however, the startervalve 62 receives pressurized air from an auxiliary power unit (APU)associated with the aircraft 8 to supply air to the starter turbine 64.The starter turbine 64 is coupled to the starter valve 62, and to thecompact accessory gearbox 60. The starter turbine 64 converts thepressurized air from the APU into rotational energy, which is used todrive the towershaft 54, which via the gears 56, 52, drives the highpressure driveshaft 46, and thus, the compressor 32 and the highpressure turbine 38 for starting the gas turbine engine 10 (FIG. 1). Thedirect-current (DC) generator 66 is coupled to the compact accessorygearbox 60, and is driven to convert mechanical energy received from thetowershaft 54 into electricity to power various electrical items onboardthe aircraft 8. The hydraulic pump 68 is coupled to the compactaccessory gearbox 60 and is driven to provide high pressure hydraulicfluid to one or more hydraulic components of the aircraft 8 and to powera hydraulically actuated thrust reverser associated with the gas turbineengine 10. The permanent magnet alternator 70 is coupled to the compactaccessory gearbox 60, and is driven to provide alternating current (AC)power to an engine control unit associated with the gas turbine engine10. The fuel control unit 72 is coupled to the compact accessory gearbox60 and is driven to provide fuel to the combustor 36 of the gas turbineengine 10 (FIG. 1). The fuel control unit 72 includes, but is notlimited to, a hydromechanical fuel control unit, an electronic fuelcontrol unit, a full authority digital engine control (FADEC), etc. Thelubrication pump 74 is coupled to the compact accessory gearbox 60 anddriven to provide oil at the desired operating pressure to variousportions of the gas turbine engine 10. With reference to FIG. 3, theair-oil separator 76 is contained wholly within the compact accessorygearbox 60, and forms part of a gear train 122 associated with thecompact accessory gearbox 60. The air-oil separator 76 is driven toseparate air from oil within the compact accessory gearbox 60.

With reference to FIG. 2, the compact accessory gearbox 60 is coupled tothe gas turbine engine 10 via one or more supports or struts 106. Inthis example, the compact accessory gearbox 60 is coupled via two struts106 a, 106 b, which extend outwardly from the compact accessory gearbox60 in a generally V-shape. The struts 106 a, 106 b are composed of asuitable high strength material, such as a metal or metal alloy. Thestruts 106 a, 106 b include one or more mounting bores 108 that receivea mechanical fastener 108 a, such as a bolt, to couple the struts 106 a,106 b to the compact accessory gearbox 60. The struts 106 a, 106 b alsoinclude a platform 110, which couples the struts 106 a, 106 b to the gasturbine engine 10. For example, the platform 110 may define one or boresfor receipt of a mechanical fastener to couple the struts 106 a, 106 bto the gas turbine engine 10. Alternatively, the platform 110 mayprovide a surface for spot welding the struts 106 a, 106 b. As a furtherexample, the platform 110 may be received in slots or interference-fitinto a portion of the gas turbine engine 10.

With reference to FIG. 3, a bottom view of the compact accessory system12 is shown with the adaptors 80 removed from the accessories 62-74 forclarity. The compact accessory gearbox 60 includes the housing or gearcase 120 and the gear train 122. In this example, the gear case 120comprises a two-piece housing, with a first portion 124 and a secondportion 126 (FIG. 9; the second portion 126 is removed in FIG. 3 toillustrate the gear train 122). The gear case 120 is composed of ametal, metal alloy or composite. The first portion 124 and the secondportion 126 are formed through any suitable technique, such as casting,forging, machining, stamping, fiber layup, etc. Generally, the firstportion 124 comprises the plurality of apertures 128 to couple the geartrain 122 to the various accessories 64-72. In this example, the firstportion 124 includes about seven apertures 128; however, the firstportion 124 may include any desired number of apertures 128. Theplurality of apertures 128 are defined about the first portion 124 so asto extend about a perimeter of the first portion 124, such that theaccessories 62-74 are arranged about a perimeter of the first portion124. Generally, the accessories 62-74 are arranged substantiallycircumferentially about the first portion 124, which enables for areduction in the volume of the engine nacelle N.

One or more of the plurality of apertures 128 is sized and shaped toreceive a bearing assembly 130. With reference to FIG. 7, the bearingassembly 130 includes a housing 132, a first bearing 134 and a secondbearing 136. The housing 132 includes a lip 138, an annular flange 140and a body 142. The housing 132 is circumferentially open and receivesthe first bearing 134 and the second bearing 136. The lip 138 is definedat a first end 132 a of the housing 132, and has a reduced wallthickness compared to the body 142 to enable the lip 138 to be receivedthrough the respective aperture 128 of the first portion 124 of the gearcase 120. The annular flange 140 extends circumferentially about thehousing 132 and defines a plurality of coupling bores 140 a. In thisexample, the annular flange 140 defines about three coupling bores 140a; however, the annular flange 140 may define any number of couplingbores 140 a. The coupling bores 140 a are generally spaced apart about aperimeter of the annular flange 140. The coupling bores 140 a receive asuitable mechanical fastener, such as a bolt, screw, rivet, etc. tocouple the bearing assembly 130 to the gear case 120. The body 142 issubstantially cylindrical, and receives the first bearing 134 and thesecond bearing 136. The body 142 includes a retaining flange 142 a,which is defined at a second end 132 b of the housing 132. The retainingflange 142 a has a diameter, which is less than a diameter of a reminderof the housing 132 to retain the first bearing 134 within the housing132. One skilled in the art would appreciate that the body 142 may bedesigned and manufactured with any shape to properly interface with anyparticular accessory 62-74.

The first bearing 134 and the second bearing 136 enable the rotation ofa portion of the gear train 122 to transfer torque between thetowershaft 54, sleeve 55 and the respective one of the accessories62-74. The first bearing 134 and the second bearing 136 are generallyball bearings or a combination of roller and ball bearings thatcooperate to receive a portion of the gear train 122 therethrough toenable the portion of the gear train 122 to rotate relative to the gearcase 120. The first bearing 134 generally includes a seal 134 a, whichfaces the retaining flange 142 a of the housing 132 when the firstbearing 134 is coupled to the housing 132. Generally, the second bearing136 does not include a seal. By not including a seal with the secondbearing 136, oil contained within the gear case 120 may lubricate boththe first bearing 134 and the second bearing 136, while the seal 134 aof the first bearing 134 prevents the leakage of oil outside of thecompact accessory gearbox 60. With reference to FIG. 8, a top view ofthe compact accessory gearbox 60 illustrates that the bearing assemblies130 are generally coupled to each of the apertures 128, with theexception of the aperture 128′, which uses a different bearingconfiguration.

With reference to FIG. 9, the second portion 126 is shown in greaterdetail. The second portion 126 may be generally planar and is removablycoupled to the first portion 124. In one example, the first portion 124is coupled to the second portion 126 via a plurality of fastening boresthat receive mechanical fasteners, such as bolts, screws, etc. (notshown); however, the first portion 124 and the second portion 126 may becoupled together via any suitable technique.

With reference back to FIG. 3, the gear train 122 is coupled to therespective accessories 64-72. The gear train 122 includes the shaft 150,a first accessory drive shaft 152, a second accessory drive shaft 154, athird accessory drive shaft 156 and a fourth accessory drive shaft 158.As will be discussed in greater detail herein, the gear 58 of thetowershaft 54 is coupled to or meshingly engages with the shaft 150, andthe shaft 150 is coupled to or meshingly engages with the firstaccessory drive shaft 152, the second accessory drive shaft 154, thethird accessory drive shaft 156 and the fourth accessory drive shaft158. As shown in FIG. 3, the first accessory drive shaft 152 drives thelubrication pump 74, the second accessory drive shaft 154 drives thefuel control unit 72, the third accessory drive shaft 156 drives thehydraulic pump 68 and the fourth accessory drive shaft 158 drives the DCgenerator 66. The shaft 150 is driven by the starter turbine 64 duringengine start-up, and drives the permanent magnet alternator 70. Thestarter turbine 64 is generally decoupled from the shaft 150 after thestart-up of the gas turbine engine 10 by an overspeed clutch. The shaft150 also defines the air-oil separator 76.

With reference to FIG. 10, the gear train 122 is shown without the gearcase 120, the bearing assembly 130, the adaptors 80, the housing 59 andthe accessories 62-74 for clarity. As shown, the shaft 150 has a shaftaxis of rotation LR, which is substantially transverse to the axis ofrotation TR of the towershaft 54. The axis of rotation LR of the shaft150 is substantially parallel to the axis of rotation R of the gasturbine engine 10 (FIG. 1). In certain embodiments, however, the axis ofrotation LR of the shaft 150 may not be substantially parallel to theaxis of rotation R. The first accessory drive shaft 152 has a firstaccessory axis of rotation R1, which is substantially transverse to theaxis of rotation LR of the shaft 150. The second accessory drive shaft154 has a second accessory axis of rotation R2, which is substantiallytransverse or oblique to the axis of rotation LR of the shaft 150, andsubstantially transverse or oblique to the first accessory axis ofrotation R1. The third accessory drive shaft 156 has a third accessoryaxis of rotation R3, which is substantially transverse or oblique to theaxis of rotation LR of the shaft 150, and is substantially transverse tothe first accessory axis of rotation R1. The third accessory axis ofrotation R3 is also substantially transverse to the second accessoryaxis of rotation R2, and intersects the second accessory axis ofrotation R2 along the axis of rotation LR of the shaft 150. The fourthaccessory drive shaft 158 has a fourth accessory axis of rotation R4,which is substantially transverse or oblique to the axis of rotation LRof the shaft 150, and is substantially transverse to the third accessoryaxis of rotation R3. The fourth accessory axis of rotation R4 issubstantially transverse to the first accessory axis of rotation R1, andintersects the first accessory axis of rotation R1 along the axis ofrotation LR of the shaft 150. The fourth accessory axis of rotation R4is substantially transverse to the second axis of rotation R2.

Each of the first accessory axis of rotation R1, the second accessoryaxis of rotation R2, the third accessory axis of rotation R3 and thefourth accessory axis of rotation R4 define the centerlines for therespective accessory drive shafts 152-158. The shaft axis of rotation LRdefines the central axis for the shaft 150. With reference to FIGS. 10Aand 10B, the first accessory axis of rotation R1, the accessory axis ofrotation R2, the third accessory axis of rotation R3 and the fourthaccessory axis of rotation R4 all substantially fit within an imaginarycone N. In this example, the cone N has an angle that ranges from aboutzero degrees (a flat disk) to about 20 degrees. In one example, the coneN has an angle of about 12.5 degrees. The shaft 150 and the shaft axisof rotation LR are generally not on this cone N, as shown. By definingthe first accessory axis of rotation R1, the accessory axis of rotationR2, the third accessory axis of rotation R3 and the fourth accessoryaxis of rotation R4 on the cone N, the accessories 62-74 are mountedsubstantially circumferentially around the compact accessory gearbox 60.In this example, the first accessory axis of rotation R1 intersects theshaft axis of rotation LR at a first point P1, and the fourth accessoryaxis of rotation R4 intersects the shaft axis of rotation LR at a secondpoint P2. Two of the accessory axes of rotation (i.e. the secondaccessory axis of rotation R2 and the third accessory axis of rotationR3) intersect the shaft axis of rotation LR at a third point P3. Thepoint P1 is different than the point P2, and is spaced apart from thepoint P2 along the shaft axis of rotation LR. The point P3 is differentthan the points P1 and P2, and is spaced apart from the points P1 and P2along the shaft axis of rotation LR.

As best shown in FIG. 8, the first accessory axis of rotation R1 isspaced apart along the perimeter of the gear case 120 from the secondaccessory axis of rotation R2 by an angle α. In one example, the angle αis about 67 degrees to about 87 degrees. Similarly, the third accessoryaxis of rotation R3 is spaced apart along the perimeter of the gear case120 from the fourth accessory axis of rotation R4 by the angle α. Thesecond accessory axis of rotation R2 is spaced apart from the shaft axisof rotation LR by an angle β. In one example, the angle β is about 41degrees to about 61 degrees. Similarly, the third accessory axis ofrotation R3 is spaced apart from the shaft axis of rotation LR by theangle β. Thus, the accessory drive shafts 152-158 are generally spacedapart about the gear case 120 in a substantially circular manner, whichresults in the placement of the accessories 62-74 substantiallycircumferentially about the gear case 120, allowing for a reduction in aspace required in the engine nacelle N for the accessories 62-74.

With additional reference to FIG. 9, one or more of the accessory axesof rotation R1-R4 may be angled relative to the shaft axis of rotationLR. For example, each of the first accessory axis of rotation R1, thesecond accessory axis of rotation R2, the third accessory axis ofrotation R3 and the fourth accessory axis of rotation R4 are angularlyoffset from the shaft axis of rotation LR by an angle γ. Stated anotherway, each of the first accessory axis of rotation R1, the secondaccessory axis of rotation R2, the third accessory axis of rotation R3and the fourth accessory axis of rotation R4 are offset relative to anaxis A of the compact accessory gearbox 60 by the angle γ. In oneexample, the angle γ is about 10 degrees to about 30 degrees. By anglingeach of the first accessory drive shaft 152, the second accessory driveshaft 154, the third accessory drive shaft 156 and the fourth accessorydrive shaft 158 relative to the shaft 150, additional space saving maybe achieved within the engine nacelle N by enabling the accessories62-74 to better follow the curvature of the gas turbine engine 10.

With reference to FIG. 10, the shaft 150 is directly coupled to thetowershaft 54, and comprises a high speed shaft. For example, the shaft150 rotates at about 18,500 revolutions per minute (rpm). The shaft 150includes a first shaft gear 160, a second shaft gear 162, a third shaftgear 164 and a fourth shaft gear 166 each arranged on and coupled to abody 168 of the shaft 150. In one example, the first shaft gear 160,second shaft gear 162, third shaft gear 164, fourth shaft gear 166 arecoupled to the body 168 via a splined joint, however, the first shaftgear 160, second shaft gear 162, third shaft gear 164, fourth shaft gear166 can be coupled to the body 168 via any technique, including, but notlimited to, keyway, welding, machined as one piece, 3D printed, etc. Thefirst shaft gear 160, second shaft gear 162, third shaft gear 164,fourth shaft gear 166 and the body 168 are generally formed of a metalor metal alloy, and may be cast, machined, forged, etc. In this example,the first shaft gear 160, second shaft gear 162, third shaft gear 164and fourth shaft gear 166 each comprise bevel gears having a respectiveplurality of bevel gear teeth 160 a, 162 a, 164 a, 166 a. The pluralityof bevel gear teeth 160 a-166 a are defined about a perimeter orcircumference of each of the shaft gears 160-166. The plurality of bevelgear teeth 160 a of the first shaft gear 160 are coupled to andmeshingly engage with the plurality of bevel gear teeth 58 a of the gear58 of the towershaft 54 and the sleeve 55. The plurality of bevel gearteeth 162 a of the second shaft gear 162 are coupled to and meshinglyengage with a plurality of bevel gear teeth 172 a of a first accessorygear 172 coupled to the first accessory drive shaft 152. The pluralityof bevel gear teeth 164 a of the third shaft gear 164 are coupled to andmeshingly engage with a plurality of bevel gear teeth 178 a of a fourthaccessory gear 178 coupled to the fourth accessory drive shaft 158. Theplurality of bevel gear teeth 166 a of the fourth shaft gear 166 arecoupled to and meshingly engage with a plurality of bevel gear teeth 174a of a second accessory gear 174 coupled to the second accessory driveshaft 154, and are coupled to and meshingly engage with a plurality ofbevel gear teeth 176 a of a third accessory gear 176 coupled to thethird accessory drive shaft 156. In one example, the first shaft gear160 also includes a projection 160 b, which aids in coupling the shaft150 to the gear case 120. Similarly, the fourth shaft gear 166 includesa projection 166 b, which aids in coupling the shaft 150 to the gearcase 120.

One or more of the shaft gears 160-166 may be separated by one or morespacers 180. In this example, the first shaft gear 160 and the secondshaft gear 162 are separated by a spacer 180 a, and the second shaftgear 162 and the third shaft gear 164 are separated by a spacer 180 b.The spacer 180 a may have a length along the shaft axis of rotation LR,which is greater than a length of the spacer 180 b along the shaft axisof rotation LR. The spacers 180 a, 180 b may be composed of any suitablematerial, such as a metal or metal alloy, and may be stamped, cast,machined, etc. The spacers 180 a, 180 b provide clearance for thecoupling of the gear 58, the first accessory gear 172 and the fourthaccessory gear 178 for rotation with the shaft 150.

With reference to FIG. 11, the body 168 of the shaft 150 includes afirst coupling portion 182, a second coupling portion 184 and theair-oil separator 76 defined between a first end 168 a and a second end168 b of the body 168. The first end 168 a of the body 168 is coupled tothe starter turbine 64, and the second end 168 b of the body 168 iscoupled to the permanent magnet alternator 70. The body 168 of the shaft150 is formed of a metal or metal alloy, and may be cast, machined,stamped, forged, etc. In one example, the first coupling portion 182extends for a first distance along a longitudinal axis L4 of the shaft150, which is different than a second distance that the second couplingportion 184 extends along the longitudinal axis L4. In this example, thefirst distance is greater than the second distance. The first couplingportion 182 includes a first enlarged portion 186 and a first pluralityof splines 188. The first enlarged portion 186 is defined adjacent tothe air-oil separator 76, and may be defined by material removal along aremainder of the body 168. In this regard, the first enlarged portion186 generally has a larger diameter than a remainder of the body 168,with the exception of a second enlarged portion 190 associated with thesecond coupling portion 184. The first enlarged portion 186 and thesecond enlarged portion 190 each have substantially the same diameterD1, which is different than a diameter D2 of the remainder of the body168. In this example, the diameter D1 is greater than the diameter D2.The first enlarged portion 186 and the second enlarged portion 190provide stops that prevent the further advancement of the third shaftgear 164 and the fourth shaft gear 166 respectively, along the body 168during assembly of the third shaft gear 164 and the fourth shaft gear166 to the body 168. Thus, each of the third shaft gear 164 and thefourth shaft gear 166 have an inner diameter, which is less than thediameter D1.

The first plurality of splines 188 are defined slightly past the firstenlarged portion 186 so as to extend slightly beyond the first enlargedportion 186 (i.e. the first plurality of splines 188 extend past thefirst enlarged portion 186 so as to abut the air-oil separator 76) andthrough the first enlarged portion 186 towards the first end 168 a ofthe body 168. Generally, the first plurality of splines 188 extend for alength along the longitudinal axis L4 that enables the first shaft gear160, spacer 180 a, second shaft gear 162, spacer 180 b and third shaftgear 164 to be coupled to the body 168. In this regard, each of thefirst shaft gear 160, spacer 180 a, second shaft gear 162, spacer 180 band third shaft gear 164 include a plurality of mating splines 192. Eachof the plurality of mating splines 192 cooperate with the firstplurality of splines 188 to couple the first shaft gear 160, spacer 180a, second shaft gear 162, spacer 180 b and third shaft gear 164 to thebody 168, while inhibiting relative rotation between the body 168 andthe first shaft gear 160, spacer 180 a, second shaft gear 162, spacer180 b and third shaft gear 164. Stated another way, the plurality ofmating splines 192 and the first plurality of splines 188 couple thefirst shaft gear 160, spacer 180 a, second shaft gear 162, spacer 180 band third shaft gear 164 to the body 168 such that the first shaft gear160, spacer 180 a, second shaft gear 162, spacer 180 b and third shaftgear 164 rotate with the body 168.

The plurality of splines 188 comprise any number of splines definedabout a circumference of the shaft 150, and may comprise a singlespline, if desired. Generally, the plurality of splines 188 are definedby machining or cutting the plurality of splines 188 into the body 168,however, the plurality of splines 188 may be formed through any desiredtechnique. The plurality of mating splines 192 may be defined along aninner diameter of each of the first shaft gear 160, spacer 180 a, secondshaft gear 162, spacer 180 b and third shaft gear 164 during theformation of the first shaft gear 160, spacer 180 a, second shaft gear162, spacer 180 b and third shaft gear 164. It will be understood,however, that the spacer 180 a and/or the spacer 180 b need not includethe plurality of mating splines 192, and can comprise a generally smoothor uniform inner diameter. Generally, the plurality of mating splines192 extend along an entirety of the inner diameter of each of the firstshaft gear 160, spacer 180 a, second shaft gear 162, spacer 180 b andthird shaft gear 164 to facilitate the advancement of each of the firstshaft gear 160, spacer 180 a, second shaft gear 162, spacer 180 b andthird shaft gear 164 along the first coupling portion 182. It should benoted that while the first shaft gear 160, spacer 180 a, second shaftgear 162, spacer 180 b and third shaft gear 164 are each describedherein as including the plurality of mating splines 192, the first shaftgear 160, spacer 180 a, second shaft gear 162, spacer 180 b and thirdshaft gear 164 may include any number of mating splines 192 thatcooperate to couple the first shaft gear 160, spacer 180 a, second shaftgear 162, spacer 180 b and third shaft gear 164 to the body 168.Moreover, the plurality of mating splines 192 may be formed to have aninterference fit with the first plurality of splines 188, if desired.

The second coupling portion 184 includes the second enlarged portion 190and a second plurality of splines 194. The second enlarged portion 190is defined adjacent to the air-oil separator 76, and is defined so to besubstantially opposite the first enlarged portion 186. The secondenlarged portion 190 may be defined by material removal along aremainder of the body 168. The second plurality of splines 194 aredefined slightly past the second enlarged portion 190 so as to extendslightly beyond the second enlarged portion 190 (i.e. the secondplurality of splines 194 extend past the second enlarged portion 190 soas to abut the air-oil separator 76) and through the second enlargedportion 190 towards the second end 168 b of the body 168. Generally, thesecond plurality of splines 194 extend for a length along thelongitudinal axis L4 that enables the fourth shaft gear 166 to becoupled to the body 168. In this regard, generally, the fourth shaftgear 166 includes a second plurality of mating splines 196. Each of thesecond plurality of mating splines 196 cooperate with the secondplurality of splines 194 to couple the fourth shaft gear 166 to the body168, while inhibiting relative rotation between the body 168 and thefourth shaft gear 166. Stated another way, the second plurality ofmating splines 196 and the second plurality of splines 194 couple thefourth shaft gear 166 to the body 168 such that the fourth shaft gear166 rotates with the body 168.

The second plurality of splines 194 comprise any number of splinesdefined about a circumference of the shaft 150, and may comprise asingle spline, if desired. Generally, the second plurality of splines194 are defined by machining or cutting the second plurality of splines194 into the body 168, however, the second plurality of splines 194 maybe formed through any desired technique. The second plurality of matingsplines 196 may be defined along an inner diameter the fourth shaft gear166 during the formation of the fourth shaft gear 166. Generally, thesecond plurality of mating splines 196 extend along an entirety of theinner diameter of the fourth shaft gear 166 to facilitate theadvancement of the fourth shaft gear 166 along the second couplingportion 184. It should be noted that while the fourth shaft gear 166 isdescribed herein as including the second plurality of mating splines196, the fourth shaft gear 166 may include any number of mating splines196 that cooperate to couple the fourth shaft gear 166 to the body 168.Moreover, the second plurality of mating splines 196 may be formed tohave an interference fit with the second plurality of splines 194, ifdesired.

The air-oil separator 76 is defined through the body 168 between thefirst coupling portion 182 and the second coupling portion 184. In thisexample, the air-oil separator 76 comprises a plurality of bores 198defined through the body 168 such that each of the plurality of bores198 are in communication with an inner channel 200 defined in the body168, as shown in FIG. 12. In this regard, the body 168 comprises asubstantially hollow shaft from the second enlarged portion 190 to thefirst end 168 a of the body 168. Stated another way, the body 168 ismilled or bored to define the inner channel 200, which extends throughthe body 168 from the first end 168 a to the second enlarged portion190. The inner channel 200 enables the separation of the air from theoil within the gear case 120 as the shaft 150 rotates within the gearcase 120. Generally, the plurality of bores 198 centrifugates oil fromthe air, with the air separated from the oil remaining within the innerchannel 200 to be drawn from the gear case 120 via a plurality of bores204 defined near the first end 168 a of the shaft 150. An additionalmesh or screen 222 may be packed inside of the inner channel 200 toincrease an available surface area within the inner channel 200, whichimproves the air oil separation effectiveness. The plurality of bores198 are generally defined about an entirety of the circumference of thebody 168 to define the air-oil separator 76, and may be arranged in arepeating pattern, or may be uniquely defined as desired along thecircumference. A sump pump (not shown) may be coupled to the gear case120 to remove the separated oil that generally collects along a surface126 a of the second portion 126 of the gear case 120. In certainexamples, the body 168 may also define a second counterbore or innerchannel 202 defined from the second end 168 b to the second couplingportion 184 to reduce a weight of the shaft 150. The second counterboreor inner channel 202 may be defined into the body 168 via milling orboring at the second end 168 b to the second coupling portion 184.

With reference back to FIG. 11, the body 168 also includes the pluralityof bores 204 defined near the first end 168 a. The air separated by theair-oil separator 76 flows from the plurality of bores 198 through theinner channel 200 to the plurality of bores 204. The air exits the shaft150, and thus, the gear case 120 via the plurality of bores 204. Theplurality of bores 204 are in communication with the inner channel 200and a shaft bearing assembly 206 to bleed air collected by the air-oilseparator 76 out of the gear case 120. In this regard, with additionalreference to FIG. 12, the shaft 150 may be assembled within the gearcase 120 with one of the bearing assemblies 130 coupled about or nearthe second end 168 b to couple the shaft 150 within the gear case 120for rotation, while the first end 168 a may be coupled to the gear case120 via the shaft bearing assembly 206 for rotation. In one example, thebearing assembly 130 bears against the projection 166 b of the fourthshaft gear 166 when the bearing assembly 130 is coupled to the gear case120 and the shaft 150 to maintain the assembly of the shaft 150 withinthe gear case 120. The bearing assembly 206 bears against the projection160 b of the first shaft gear 160 when the bearing assembly 206 iscoupled to the gear case 120 to maintain the assembly of the shaft 150within the gear case 120.

As the shaft bearing assembly 206 may be substantially similar to thebearing assembly 130 described with regard to FIG. 7, the same referencenumerals will be used to denote the same or similar components. In oneexample, the shaft bearing assembly 206 includes a housing 208, thefirst bearing 134, the second bearing 136 and a spacer 210. The housing208 includes the lip 138, the annular flange 140 and a body 212. Thehousing 208 is circumferentially open and receives the first bearing 134and the second bearing 136. The lip 138 is defined at a first end 208 aof the housing 208, and the annular flange 140 extends circumferentiallyabout the housing 208 and defines the plurality of coupling bores 140 a.The body 212 is substantially cylindrical, and receives the firstbearing 134 and the second bearing 136. The body 212 includes aretaining flange 212 a, which is defined at a second end 208 b of thehousing 208. The retaining flange 212 a has a diameter, which is lessthan a diameter of a reminder of the housing 208 to retain the firstbearing 134 within the housing 208.

The spacer 210 is positioned between the first bearing 134 and thesecond bearing 136 within the housing 208. The spacer 210 includes aplurality of slots 210 a defined about a circumference of the spacer210, which are in fluid communication with the plurality of bores 204 ofthe body 168, as shown in FIG. 12. The plurality of slots 210 a enablethe air collected via the air-oil separator 76 to be bleed out of thecompact accessory gearbox 60, as the spacer 210 is located external tothe gear case 120 when the bearing assembly 206 is coupled to the gearcase 120.

With reference back to FIG. 10, the first accessory drive shaft 152, thesecond accessory drive shaft 154, the third accessory drive shaft 156and the fourth accessory drive shaft 158 are each coupled directly tothe shaft 150 to be driven directly by the shaft 150. Each of the firstaccessory drive shaft 152, the second accessory drive shaft 154, thethird accessory drive shaft 156 and the fourth accessory drive shaft 158are composed of a suitable metal or metal alloy, and may be cast,machined, forged, etc. The first accessory drive shaft 152 includes thefirst accessory gear 172 defined about a first end 152 a of the firstaccessory drive shaft 152. The first accessory gear 172 is composed of asuitable metal or metal alloy, and may be cast, machined, forged, etc.and coupled to the first accessory drive shaft 152. Further, the firstaccessory gear 172 may be integrally formed with the first accessorydrive shaft 152. The first accessory gear 172 comprises a bevel gearthat has the plurality of bevel gear teeth 172 a. The plurality of bevelgear teeth 172 a are defined about a perimeter or circumference of thefirst accessory gear 172, and the plurality of bevel gear teeth 172 ameshingly engage the plurality of bevel gear teeth 162 a of the secondshaft gear 162. The first accessory drive shaft 152 comprises a lowerspeed drive shaft, and is driven to rotate at about 8,500 rpm. Statedanother way, the first accessory drive shaft 152 rotates at a speed,which is different than a rotational speed of the shaft 150 and isgenerally less than the rotational speed of the shaft 150. The firstaccessory drive shaft 152 is coupled to the lubrication pump 74 at asecond end 152 b. The first accessory drive shaft 152 also includes abearing stop portion 214. The bearing stop portion 214 is defined as anarea along the first accessory drive shaft 152 that has an increased orgreater diameter than a reminder of the first accessory drive shaft 152to provide a stop for the bearing assembly 130. The bearing stop portion214 is defined near the first end 152 a, and when assembled into thegear case 120, the bearing stop portion 214 contacts the second bearing136 of the bearing assembly 130.

The second accessory drive shaft 154 includes the second accessory gear174 defined about a first end 154 a of the second accessory drive shaft154. The second accessory gear 174 is composed of a suitable metal ormetal alloy, and may be cast, machined, forged, etc. and coupled to thesecond accessory drive shaft 154. Further, the second accessory gear 174may be integrally formed with the second accessory drive shaft 154. Thesecond accessory gear 174 comprises a bevel gear that has the pluralityof bevel gear teeth 174 a. The plurality of bevel gear teeth 174 a aredefined about a perimeter or circumference of the second accessory gear174, and the plurality of bevel gear teeth 174 a meshingly engage theplurality of bevel gear teeth 166 a of the fourth shaft gear 166. Thesecond accessory drive shaft 154 comprises a lower speed drive shaft,and is driven to rotate at about 8,500 rpm. Stated another way, thesecond accessory drive shaft 154 rotates at a speed, which is differentthan the rotational speed of the shaft 150 and is generally less thanthe rotational speed of the shaft 150. The second accessory drive shaft154 is coupled to the fuel control unit 72 at a second end 154 b. Thesecond accessory drive shaft 154 also includes a second bearing stopportion 216. The second bearing stop portion 216 is defined as an areaalong the second accessory drive shaft 154 that has an increased orgreater diameter than a reminder of the second accessory drive shaft 154to provide a stop for the bearing assembly 130. The second bearing stopportion 216 is defined near the first end 154 a, and when assembled intothe gear case 120, the second bearing stop portion 216 contacts thesecond bearing 136 of the bearing assembly 130.

The third accessory drive shaft 156 includes the third accessory gear176 defined about a first end 156 a of the third accessory drive shaft156. The third accessory gear 176 is composed of a suitable metal ormetal alloy, and may be cast, machined, forged, etc. and coupled to thethird accessory drive shaft 156. Further, the third accessory gear 176may be integrally formed with the third accessory drive shaft 156. Thethird accessory gear 176 comprises a bevel gear that has the pluralityof bevel gear teeth 176 a. The plurality of bevel gear teeth 176 a aredefined about a perimeter or circumference of the third accessory gear176, and the plurality of bevel gear teeth 176 a meshingly engage theplurality of bevel gear teeth 166 a of the fourth shaft gear 166. Thethird accessory drive shaft 156 comprises a lower speed drive shaft, andis driven to rotate at about 8,500 rpm. Stated another way, the thirdaccessory drive shaft 156 rotates at a speed, which is different thanthe rotational speed of the shaft 150 and is generally less than therotational speed of the shaft 150. The third accessory drive shaft 156is coupled to the hydraulic pump 68 at a second end 156 b. The thirdaccessory drive shaft 156 also includes a third bearing stop portion218. The third bearing stop portion 218 is defined as an area along thethird accessory drive shaft 156 that has an increased or greaterdiameter than a reminder of the third accessory drive shaft 156 toprovide a stop for the bearing assembly 130. The third bearing stopportion 218 is defined near the first end 156 a, and when assembled intothe gear case 120, the third bearing stop portion 218 contacts thesecond bearing 136 of the bearing assembly 130.

The fourth accessory drive shaft 158 includes the fourth accessory gear178 defined about a first end 158 a of the fourth accessory drive shaft158. The fourth accessory gear 178 is composed of a suitable metal ormetal alloy, and may be cast, machined, forged, etc. and coupled to thefourth accessory drive shaft 158. Further, the fourth accessory gear 178may be integrally formed with the fourth accessory drive shaft 158. Thefourth accessory gear 178 comprises a bevel gear that has the pluralityof bevel gear teeth 178 a. The plurality of bevel gear teeth 178 a aredefined about a perimeter or circumference of the fourth accessory gear178, and the plurality of bevel gear teeth 178 a meshingly engages theplurality of bevel gear teeth 164 a of the third shaft gear 164. Thefourth accessory drive shaft 158 comprises a high speed drive shaft, andis driven to rotate at about 18,500 rpm. Stated another way, the fourthaccessory drive shaft 158 rotates at a speed, which is about the same asthe rotational speed of the shaft 150. Thus, generally, the fourthaccessory gear 178 has a diameter that is different or greater than adiameter of the first accessory gear 172, second accessory gear 174 andthird accessory gear 176. The fourth accessory drive shaft 158 iscoupled to the DC generator 66 at a second end 158 b. The fourthaccessory drive shaft 158 also includes a fourth bearing stop portion220. The fourth bearing stop portion 220 is defined as an area along thefourth accessory drive shaft 158 that has an increased or greaterdiameter than a remainder of the fourth accessory drive shaft 158 toprovide a stop for the bearing assembly 130. The fourth accessory driveshaft 158 is defined near the first end 158 a, and when assembled intothe gear case 120, the fourth accessory drive shaft 158 contacts thesecond bearing 136 of the bearing assembly 130.

Generally, the gear case 120 is not filled with oil to lubricate thegear train 122. In this example, with reference to FIGS. 1B and 13, oilor lubricating fluid for the compact accessory gearbox 60 is alsoreceived from an oil tank 232. The oil tank 232 is disposed near thecompact accessory gearbox 60 within the engine nacelle N. One or moreconduits are coupled between the oil tank 232 and the compact accessorygearbox 60 to enable oil from the oil tank 232 to flow to the gear case120 to lubricate the gear train 122. In FIG. 1B, the oil is contained inthe oil tank 232, and flows to the oil pump 74, through an oil filter234, and through an air/oil cooler 235 that delivers the oil orlubricating fluid to the gear case 120 of the compact accessory gearbox60 to lubricate the gear train 122. The oil is scavenged from thecompact accessory gearbox 60 and returns to the oil tank 232. Thus, theoil tank 232 and the compact accessory gearbox 60 may include one ormore fittings, hoses, control valves and ports, which fluidly couple theconduits to the oil tank 232 and the compact accessory gearbox 60. Inthis example, the oil tank 232 is separate from the compact accessorygearbox 60. With reference to FIG. 13, the oil tank 232 may include theoil filter 234, a fuel heater/oil cooler 236 and some accessories,including, plugs, fittings, hoses and ports (not shown).

In order to assemble the shaft 150, in one example, with the body 168 ofthe shaft 150 machined to include the first coupling portion 182, thesecond coupling portion 184 and the air-oil separator 76, the thirdshaft gear 164 is slid over the first end 168 a of the body 168 untilthe third shaft gear 164 abuts the first enlarged portion 186. Thefourth shaft gear 166 is slid over the second end 168 b of the body 168until the fourth shaft gear 166 abuts the second enlarged portion 190.The spacer 180 b is slid over the first end 168 a until the spacer 180 babuts the third shaft gear 164. The second shaft gear 162 is slid overthe first end 168 a until the second shaft gear 162 abuts the spacer 180b. The spacer 180 a is slid over the first end 168 a until the spacer180 a abuts the second shaft gear 162. The first shaft gear 160 is slidover the first end 168 a until the first shaft gear 160 abuts the spacer180 a.

In one example, in order to assemble the compact accessory gearbox 60,the first accessory drive shaft 152, the second accessory drive shaft154, the third accessory drive shaft 156 and the fourth accessory driveshaft 158 are each positioned through a respective one of the pluralityof apertures 128 defined through the first portion 124 of the gear case120. Respective ones of the bearing assemblies 130 are coupled to eachof the first accessory drive shaft 152, the second accessory drive shaft154, the third accessory drive shaft 156 and the fourth accessory driveshaft 158, and are slid over the respective second ends 152 b, 154 b,156 b, 158 b until the bearing assembly 130 contacts the respectivebearing stop portion 214, 216, 218, 220. Upon contacting the bearingstop portions 214, 216, 218, 220, a plurality of mechanical fastenersare inserted through the coupling bores 140 a to couple the bearingassemblies 130 to the first portion 124, thereby coupling the firstaccessory drive shaft 152, the second accessory drive shaft 154, thethird accessory drive shaft 156 and the fourth accessory drive shaft 158to the first portion 124 of the gear case 120.

With the shaft 150 assembled, the shaft 150 is inserted through theaperture 128″ until the fourth shaft gear 166 contacts a surface of thefirst portion 124. The bearing assembly 130 is slid over the second end168 b of the body 168 and the bearing assembly 206 is slid over thefirst end 168 a of the body 168 such that the plurality of bores 204 arealigned with the plurality of slots 210 a in the spacer 210 to enableair to vent from the gear case 120. A plurality of mechanical fastenersare inserted into the coupling bores 140 a to couple the bearingassembly 130 and the bearing assembly 206 to the first portion 124 ofthe gear case 120. The second portion 126 is positioned over the firstportion 124 and coupled to the first portion 124 via one or moremechanical fasteners.

With the first portion 124 and the second portion 126 of the gear case120 coupled together, the gear case 120 is positioned such that thesecond end 54 b of the towershaft 54 is received within the aperture128′ and the gear 58 of the sleeve 55 meshingly engages with the shaft150. The housing 59 of the towershaft 54 is coupled to the first portion124 of the gear case 120 via one or more mechanical fasteners, and thestruts 106 a, 106 b are coupled to the gas turbine engine 10 to couplethe compact accessory gearbox 60 to the gas turbine engine 10.

With the compact accessory gearbox 60 coupled to the gas turbine engine10, the accessories 62-74 are coupled to the first accessory drive shaft152, the second accessory drive shaft 154, the third accessory driveshaft 156, the fourth accessory drive shaft 158 and the shaft 150 viathe adaptors 80. The compact accessory gearbox 60 has a volume that isabout 1/18^(th) the size of a conventional gearbox, and provides about a93 percent reduction in space required within the engine nacelle N forthe compact accessory gearbox 60 when compared to a conventionalgearbox.

In one example, with the high pressure driveshaft 46 driving or rotatingthe towershaft 54 about the towershaft axis of rotation TR, the torquefrom the high pressure driveshaft 46 is transmitted through thetowershaft 54 and into the gear train 122 via the meshing engagement ofthe gear 58 with the first shaft gear 160. Thus, the rotation of thetowershaft 54 rotates the shaft 150 about the shaft axis of rotation LR.The rotation of the shaft 150 drives or rotates the first accessorydrive shaft 152 (via the engagement between the second shaft gear 162and the first accessory gear 172); drives or rotates the secondaccessory drive shaft 154 (via the engagement between the fourth shaftgear 166 and the second accessory gear 174); drives or rotates the thirdaccessory drive shaft 156 (via the engagement between the fourth shaftgear 166 and the third accessory gear 176); and drives or rotates thefourth accessory drive shaft 158 (via the engagement between the thirdshaft gear 164 and the fourth accessory gear 178). The rotation of theshaft 150 also separates the air from the oil within the compactaccessory gearbox 60, which is bled out through the plurality of bores204 and slots 210 a. The rotation of the drive shafts 152-158 providesinput torque the respective accessories 74, 72, 68 and 66 for operatingthe respective accessories 74, 72, 68 and 66. Moreover, the rotation ofthe shaft 150 provides input torque to the permanent magnet alternator70.

Prior to a start-up of the gas turbine engine 10, the starter valve 62may direct pressurized air to the starter turbine 64. The starterturbine 64 rotates the shaft 150, and the engagement between the firstshaft gear 160 and the gear 58 transmits the torque from the starterturbine 64 to the high pressure driveshaft 46, which causes the highpressure driveshaft 46 to rotate. The rotation of the high pressuredriveshaft 46 drives the compressor 32 and the high pressure turbine 38,thereby enabling a start-up of the gas turbine engine 10.

It should be noted that the compact accessory gearbox 60 may beconfigured in various different ways. For example, with reference toFIG. 14, a simplified view of a compact accessory gearbox 300 is shownin which the bearing assemblies 130, 206, adaptors 80 and accessories62-74 are removed for clarity. As the compact accessory gearbox 300 issimilar to the compact accessory gearbox 60 discussed with regard toFIGS. 1-13, only the differences between the compact accessory gearbox300 and the compact accessory gearbox 60 will be discussed in detailherein, with the same reference numerals used to denote the same orsubstantially similar components. The compact accessory gearbox 300 canbe employed with the gas turbine engine 10 to transmit torque from thetowershaft 54 to the accessories 64-74.

The compact accessory gearbox 300 includes the gear case 120 and a geartrain 302. The gear train 302 is coupled to the respective accessories64-74. Similar to the compact accessory gearbox 60, the accessories62-74 are arranged substantially circumferentially about the firstportion 124 of the compact accessory gearbox 300, which enables for areduction in the volume of the engine nacelle N. The gear train 302includes a shaft 304, a first accessory drive shaft 306, a secondaccessory drive shaft 314, a third accessory drive shaft 308, a fourthaccessory drive shaft 310 and a fifth accessory drive shaft 312. As willbe discussed in greater detail herein, the gear 58 of the sleeve 55 iscoupled to or meshingly engages with the shaft 304, and the shaft 304 iscoupled to or meshingly engages with the first accessory drive shaft 306and the second accessory drive shaft 314. Generally, the first accessorydrive shaft 306 drives the lubrication pump 74, the third accessorydrive shaft 308 drives the fuel control unit 72, the fourth accessorydrive shaft 310 drives the drives the permanent magnet alternator 70,the fifth accessory drive shaft 312 drives the hydraulic pump 68 and thesecond accessory drive shaft 314 drives the DC generator 66. The shaft304 is driven by the starter turbine 64.

With continued reference to FIG. 14, the shaft 304 has a shaft axis ofrotation LR2, which is substantially transverse to the axis of rotationTR of the towershaft 54. The axis of rotation LR of the shaft 304 issubstantially parallel to the axis of rotation R of the gas turbineengine 10 (FIG. 1). In certain embodiments, however, the axis ofrotation LR of the shaft 304 may not be substantially parallel to theaxis of rotation R. The first accessory drive shaft 306 has a firstaccessory axis of rotation R1 a, which is substantially transverse tothe axis of rotation LR2 of the shaft 304. The third accessory driveshaft 308 has a third accessory axis of rotation R2 a, which issubstantially transverse to the axis of rotation LR2 of the shaft 304,and substantially transverse to the first accessory axis of rotation R1a. The fourth accessory drive shaft 310 has a fourth accessory axis ofrotation R3 a, which is substantially parallel to the axis of rotationLR2 of the shaft 304, and is substantially transverse to the firstaccessory axis of rotation R1 a. The fourth accessory axis of rotationR3 a is also substantially transverse to the third accessory axis ofrotation R2 a. The fifth accessory drive shaft 312 has a fifth accessoryaxis of rotation R4 a, which is substantially transverse to the axis ofrotation LR2 of the shaft 304, and is substantially transverse to thefourth accessory axis of rotation R3 a. The fifth accessory axis ofrotation R4 a is substantially transverse to the first accessory axis ofrotation R1 a. The fifth accessory axis of rotation R4 a issubstantially transverse to the third axis of rotation R2 a. The secondaccessory drive shaft 314 has a second accessory axis of rotation R5 a,which is substantially transverse to the axis of rotation LR2 of theshaft 304, and is substantially transverse to the fourth accessory axisof rotation R3 a. The second accessory axis of rotation R5 a issubstantially transverse to the third accessory axis of rotation R2 a,and is substantially transverse to the first accessory axis of rotationR1 a. The second accessory axis of rotation R5 a is substantiallytransverse to the fifth axis of rotation R4 a. In this example, each ofthe axes of rotation LR2, R1 a-R5 a, which each comprise centerlines,intersect at a single common point P. The axes of rotation TR and R5 aalso intersect each other, but may not necessarily intersect each otherat point P.

Each of the first accessory axis of rotation R1 a, the third accessoryaxis of rotation R2 a, the fourth accessory axis of rotation R3 a, thefifth accessory axis of rotation R4 a and the second accessory axis ofrotation R5 a define the centerlines for the respective accessory driveshafts 306-314. The shaft axis of rotation LR2 defines the central axisfor the shaft 304.

In this example, the first accessory axis of rotation R1 a is spacedapart along the perimeter of the gear case 120 from the third accessoryaxis of rotation R2 a by the angle α. In one example, the angle α isabout 67 degrees to about 87 degrees. Similarly, the second accessoryaxis of rotation R5 a is spaced apart along the perimeter of the gearcase 120 from the fifth accessory axis of rotation R4 a by the angle α.The third accessory axis of rotation R2 a is spaced apart from thefourth accessory axis of rotation R3 a by the angle β. Similarly, thefourth accessory axis of rotation R3 a is spaced apart from the fifthaxis of rotation R4 a by the angle β. Thus, the accessory drive shafts306-314 are generally spaced apart about the gear case 120 in asubstantially circular manner, which results in the placement of theaccessories 62-74 substantially circumferentially about the gear case120, allowing for a reduction in a space required in the engine nacelleN for the accessories 62-74. In addition, one or more of the accessoryaxes of rotation R1 a-R5 a may be angled relative to the shaft axis ofrotation LR2, if desired.

The shaft 304 is directly coupled to the sleeve 55, and comprises a highspeed shaft. For example, the shaft 304 rotates at about 18,500revolutions per minute (rpm). The shaft 304 includes a first shaft gear320, a second shaft gear 322 and a third shaft gear 324 each arranged onand coupled to a body 326 of the shaft 304. The first shaft gear 320,second shaft gear 322, third shaft gear 324 and the body 326 aregenerally formed of a metal or metal alloy, and may be cast, machined,forged, etc. In this example, the first shaft gear 320, second shaftgear 322 and third shaft gear 324 each comprise bevel gears having arespective plurality of bevel gear teeth 320 a-324 a. The plurality ofbevel gear teeth 320 a-324 a are each defined about a perimeter orcircumference of each of the shaft gears 320-324. The plurality of bevelgear teeth 320 a of the first shaft gear 320 are coupled to andmeshingly engage with the plurality of bevel gear teeth 58 a of the gear58 of the sleeve 55. The plurality of bevel gear teeth 322 a of thesecond shaft gear 322 are coupled to and meshingly engage with aplurality of bevel gear teeth 172 a of the first accessory gear 172coupled to the first accessory drive shaft 306. The plurality of bevelgear teeth 324 a of the third shaft gear 324 are coupled to andmeshingly engage with a plurality of bevel gear teeth 178 a of thefourth accessory gear 178, which is coupled to the second accessorydrive shaft 314. In one example, the first shaft gear 320 also includesa flat surface 320 b, which aids in coupling the shaft 304 to the gearcase 120 by providing a coupling surface for a respective one of thebearing assemblies 130, for example.

One or more of the shaft gears 320-324 may be separated by one or morespacers 328. In this example, the first shaft gear 320 and the secondshaft gear 322 are separated by a spacer 328 a, and the second shaftgear 322 and the third shaft gear 324 are separated by a spacer 328 b.The spacer 328 a may have a length along the shaft axis of rotation LR2,which is greater than a length of the spacer 328 b along the shaft axisof rotation LR2. The spacers 328 a, 328 b may be composed of anysuitable material, such as a metal or metal alloy, and may be stamped,cast, machined, etc. The spacers 328 a, 328 b provided clearance for thecoupling of the gear 58, the first accessory gear 172 and the fourthaccessory gear 178 for rotation with the shaft 150.

The body 326 of the shaft 304 is formed of a metal or metal alloy, andmay be cast, machined, stamped, forged, etc. Although not illustratedherein, the body 326 may include the first coupling portion 182 and thesecond coupling portion 184, if desired. The body 326 includes a firstend 326 a opposite a second end 326 b. The third shaft gear 324 iscoupled at the first end 326 a and the starter turbine 64 is coupled tothe second end 326 b.

The first accessory drive shaft 306 and the second accessory drive shaft314 are each coupled directly to the shaft 304 to be driven directly bythe shaft 304. Each of the first accessory drive shaft 306, the thirdaccessory drive shaft 308, the fourth accessory drive shaft 310, thefifth accessory drive shaft 312 and the second accessory drive shaft 314are composed of a suitable metal or metal alloy, and may be cast,machined, forged, etc. The first accessory drive shaft 306 includes thefirst accessory gear 172 defined about a first end 306 a of the firstaccessory drive shaft 306, which meshingly engages the second shaft gear322. The first accessory drive shaft 306 comprises a lower speed driveshaft, and is driven to rotate at about 8,500 rpm. Stated another way,the first accessory drive shaft 306 rotates at a speed, which isdifferent than a rotational speed of the shaft 304 and is generally lessthan the rotational speed of the shaft 304. The first accessory driveshaft 306 is coupled to the lubrication pump 74 at a second end 306 b.

The third accessory drive shaft 308 includes the second accessory gear174 defined about a first end 308 a of the third accessory drive shaft308. The second accessory gear 174 is coupled to and meshingly engagesthe first accessory gear 172. The third accessory drive shaft 308comprises a lower speed drive shaft, and is driven to rotate at about8,500 rpm. Stated another way, the third accessory drive shaft 308rotates at a speed, which is different than the rotational speed of theshaft 304 and is generally less than the rotational speed of the shaft304. The third accessory drive shaft 308 is coupled to the fuel controlunit 72 at a second end 308 b.

The fourth accessory drive shaft 310 includes a fifth accessory gear 330defined about a first end 310 a of the fourth accessory drive shaft 310.The fifth accessory gear 330 is composed of a suitable metal or metalalloy, and may be cast, machined, forged, etc. and coupled to the fourthaccessory drive shaft 310. Further, the fifth accessory gear 330 may beintegrally formed with the fourth accessory drive shaft 310. The fifthaccessory gear 330 comprises a bevel gear that has a plurality of bevelgear teeth 330 a. The plurality of bevel gear teeth 330 a are definedabout a perimeter or circumference of the fifth accessory gear 330. Theplurality of bevel gear teeth 330 a are coupled to and meshingly engagethe plurality of bevel gear teeth 174 a of the second accessory gear174, and the plurality of bevel gear teeth 330 a are coupled to andmeshingly engage the plurality of bevel gear teeth 176 a of the thirdaccessory gear 176. The fourth accessory drive shaft 310 comprises ahigh speed drive shaft, and is driven to rotate at about 18,500 rpm.Stated another way, the fourth accessory drive shaft 310 rotates at aspeed, which is about the same as the rotational speed of the shaft 304.Thus, the fifth accessory gear 330 has a diameter, which is different orless than a diameter of the first accessory gear 172, the secondaccessory gear 174 and the third accessory gear 176. The fourthaccessory drive shaft 310 is coupled to the permanent magnet alternator70 at a second end 310 b.

The fifth accessory drive shaft 312 includes the third accessory gear176 defined about a first end 312 a of the fifth accessory drive shaft312. The plurality of bevel gear teeth 176 a are coupled to andmeshingly engage the plurality of bevel gear teeth 330 a of the fifthaccessory gear 330. The fifth accessory drive shaft 312 comprises alower speed drive shaft, and is driven to rotate at about 8,500 rpm.Stated another way, the fifth accessory drive shaft 312 rotates at aspeed, which is different than the rotational speed of the shaft 304 andis generally less than the rotational speed of the shaft 304. The fifthaccessory drive shaft 312 is coupled to the hydraulic pump 68 at asecond end 312 b.

The second accessory drive shaft 314 includes the fourth accessory gear178 defined about a first end 314 a of the second accessory drive shaft314. The plurality of bevel gear teeth 178 a of the fourth accessorygear 178 are coupled to and meshingly engage the plurality of bevel gearteeth 324 a of the third shaft gear 324. The second accessory driveshaft 314 comprises a high speed drive shaft, and is driven to rotate atabout 18,500 rpm. Stated another way, the second accessory drive shaft314 rotates at a speed, which is about the same as the rotational speedof the shaft 304. A diameter of the fourth accessory gear 178 isgenerally about equal to the diameter of the second accessory gear 330;however, it will be understood that the fourth accessory gear 178 canhave a diameter that is different than the diameter of the fifthaccessory gear 330. The second accessory drive shaft 314 is coupled tothe DC generator 66 at a second end 314 b. Generally, the second shaftgear 322 and the fifth accessory gear 330 are substantially identical,and the first accessory gear 172, the second accessory gear 174, thethird accessory gear 176 are substantially identical

Similar to the compact accessory gearbox 60 described with regard toFIGS. 1-13, the gear case 120 is not filled with oil to lubricate thegear train 302. Rather, oil to lubricate the gear train 302 is providedthrough the lubrication channel 230 defined through the sleeve 55. Incertain examples, oil or lubricating fluid for the compact accessorygearbox 60 is also received from an oil tank (not shown).

In order to assemble the shaft 304, in one example, the third shaft gear324 is slid over the body 326 to the first end 326 a. The spacer 328 bis slid over the body 326 until the spacer 328 b abuts the third shaftgear 324. The second shaft gear 322 is slid over the body 326 until thesecond shaft gear 322 abuts the spacer 328 b. The spacer 328 a is slidover the body 326 until the spacer 328 a abuts the second shaft gear322. The first shaft gear 320 is slid over the body 326 until the firstshaft gear 320 abuts the spacer 328 a.

In one example, in order to assemble the compact accessory gearbox 300,the first accessory drive shaft 306, the third accessory drive shaft308, the fourth accessory drive shaft 310, the fifth accessory driveshaft 312 and the second accessory drive shaft 314 are each positionedthrough a respective one of the plurality of apertures 128 definedthrough the first portion 124 of the gear case 120. Respective ones ofthe bearing assemblies 130 are coupled to each of the first accessorydrive shaft 306, the third accessory drive shaft 308, the fourthaccessory drive shaft 310, the fifth accessory drive shaft 312 and thesecond accessory drive shaft 314, and a plurality of mechanicalfasteners are inserted through the coupling bores 140 a to couple thebearing assemblies 130 to the first portion 124, thereby coupling thefirst accessory drive shaft 306, the third accessory drive shaft 308,the fourth accessory drive shaft 310, the fifth accessory drive shaft312 and the second accessory drive shaft 314 to the first portion 124 ofthe gear case 120.

With the shaft 304 assembled, the shaft 304 is inserted through theaperture 128″ until the third shaft gear 324 meshingly engages with thefourth accessory gear 178. The bearing assembly 130 is slid over thesecond end 326 b of the body 326 and a plurality of mechanical fastenersare inserted into the coupling bores 140 a to couple the bearingassembly 130 to the first portion 124 of the gear case 120. The secondportion 126 is positioned over the first portion 124 and coupled to thefirst portion 124 via one or more mechanical fasteners. With the firstportion 124 and the second portion 126 of the gear case 120 coupledtogether, the gear case 120 is coupled to the gas turbine engine 10 asdiscussed with regard to the compact accessory gearbox 60 of FIGS. 1-13.The compact accessory gearbox 300 has a volume that is about 1/18^(th)the size of a conventional gearbox, and provides about a 93 percentreduction in space required within the engine nacelle N for the compactaccessory gearbox 300 when compared to a conventional gearbox.

In one example, with the high pressure driveshaft 46 driving or rotatingthe towershaft 54, the torque from the high pressure driveshaft 46 istransmitted through the towershaft 54, the sleeve 55 and into the geartrain 302 via the meshing engagement of the gear 58 with the first shaftgear 320. Thus, the rotation of the towershaft 54 rotates the shaft 304about the shaft axis of rotation LR2. The rotation of the shaft 304drives or rotates the first accessory drive shaft 306 (via theengagement between the second shaft gear 322 and the first accessorygear 172); and drives or rotates the second accessory drive shaft 314(via the engagement between the third shaft gear 324 and the fourthaccessory gear 178). The rotation of the first accessory gear 172 drivesor rotates the second accessory gear 174, and thus, the third accessorydrive shaft 308. The rotation of the second accessory gear 174 drives orrotates the fifth accessory gear 330, and thus, the fourth accessorydrive shaft 310. The rotation of the fifth accessory gear 330 drives orrotates the third accessory gear 176, and thus, the fifth accessorydrive shaft 312. The rotation of the drive shafts 306-314 provides inputtorque the respective accessories 74, 72, 70, 68 and 66 for operatingthe respective accessories 74, 72, 70, 68 and 66.

Prior to a start-up of the gas turbine engine 10, the starter valve 62may direct pressurized air to the starter turbine 64. The starterturbine 64 rotates the shaft 304, and the engagement between the firstshaft gear 320 and the gear 58 transmits the torque from the starterturbine 64 to the high pressure driveshaft 46, which causes the highpressure driveshaft 46 to rotate. The rotation of the high pressuredriveshaft 46 drives the compressor 32 and the high pressure turbine 38,thereby enabling a start-up of the gas turbine engine 10.

With reference to FIG. 15, a compact accessory system 400 is shown. Asthe compact accessory system 400 is similar to the compact accessorysystem 12 discussed with regard to FIGS. 1-13, only the differencesbetween the compact accessory system 400 and the compact accessorysystem 12 will be discussed in detail herein, with the same referencenumerals used to denote the same or substantially similar components.The compact accessory system 12 can be employed with the gas turbineengine 10 to transmit torque from the towershaft 54 to the accessories64-74.

In this example, the compact accessory system 400 includes a compactaccessory gearbox 402, which drives various accessories, including, butnot limited to, the starter valve 62, the starter turbine 64, thedirect-current (DC) generator 66, the hydraulic pump 68, the permanentmagnet alternator 70, the fuel control unit 72 and the lubrication pump74. Generally, the compact accessory gearbox 402 is coupled to thetowershaft 54 via the gear 58 to receive the torque from the sleeve 55and drive the accessories 62-74. It should be noted that the accessories62-74 described herein are merely exemplary, as the compact accessorygearbox 60 may be used to drive any suitable accessory associated withthe gas turbine engine 10. One or more of the accessories 64-74 can becoupled to the compact accessory gearbox 402 via the adaptor 80.

The compact accessory gearbox 402 includes a housing or gear case 404and a gear train 406 (FIG. 16). In this example, the gear case 404comprises a two-piece housing; however, the gear case 404 may comprise aone-piece housing, if desired. The gear case 404 is composed of a metalor metal alloy, which is stamped, machined or forged, etc. to define theshape of the gear case 404. Generally, the gear case 120 comprises aplurality of apertures 408 to couple the gear train 406 to the variousaccessories 64-74. The plurality of apertures 128 are defined about thegear case 404 so as to extend about a perimeter of the gear case 404,such that the accessories 62-74 are arranged about a perimeter of thegear case 404. Generally, the accessories 62-74 are arrangedsubstantially circumferentially about the gear case 404, which enablesfor a reduction in the volume of the engine nacelle N. In certaininstances, one or more bearing assemblies, such as the bearingassemblies 130, may be coupled between the accessories 62-74 and thegear case 404 to provided support for the rotation of the variousportions of the gear train 406 relative to the gear case 404.

With reference to FIG. 16, the gear train 406 is shown without the gearcase 404 and the accessories 62-74 for clarity. The gear train 406includes a shaft 410, a first accessory drive shaft 412, a secondaccessory drive shaft 414, a third accessory drive shaft 416, a fourthaccessory drive shaft 418 and a gear set 419. As shown in FIG. 15, thefirst accessory drive shaft 412 drives the fuel control unit 72, thesecond accessory drive shaft 414 drives the permanent magnet alternator70, the third accessory drive shaft 416 drives the lubrication pump 74and the fourth accessory drive shaft 418 drives the hydraulic pump 68.The shaft 410 is driven by the starter turbine 64, and drives the DCgenerator 66.

With reference to FIG. 17, the shaft 410 has a shaft axis of rotationLR3, which is substantially transverse to the axis of rotation TR of thetowershaft 54. In one example, the axis of rotation TR of the towershaft54 is angularly offset from the shaft axis of rotation LR3 by an angleδ. The angle δ is about 53 degrees to about 93 degrees. With referenceback to FIG. 16, the axis of rotation LR3 of the shaft 410 issubstantially parallel to the axis of rotation R of the gas turbineengine 10 (FIG. 1). The first accessory drive shaft 412 has a firstaccessory axis of rotation Rib, which is substantially transverse to theaxis of rotation LR3 of the shaft 410. The second accessory drive shaft414 has a second accessory axis of rotation R2 b, which is substantiallytransverse to the axis of rotation LR3 of the shaft 410, andsubstantially transverse to the first accessory axis of rotation R1 b.The third accessory drive shaft 416 has a third accessory axis ofrotation R3 b, which is substantially transverse to the axis of rotationLR3 of the shaft 410, and is substantially parallel to the firstaccessory axis of rotation R1 b. The third accessory axis of rotation R3b is also substantially transverse to the second accessory axis ofrotation R2 b. The fourth accessory drive shaft 418 has a fourthaccessory axis of rotation R4 b, which is substantially transverse tothe axis of rotation LR3 of the shaft 410, and is substantiallytransverse to the third accessory axis of rotation R3 b. The fourthaccessory axis of rotation R4 b is substantially transverse to the firstaccessory axis of rotation R1 b. The fourth accessory axis of rotationR4 b is substantially parallel to the second axis of rotation R2 b. Eachof the first accessory axis of rotation Rib, the second accessory axisof rotation R2 b, the third accessory axis of rotation R3 b and thefourth accessory axis of rotation R4 b define the centerlines for therespective accessory drive shafts 412-418. The shaft axis of rotationLR3 defines the central axis for the shaft 410. Further, in thisexample, the first accessory axis of rotation Rib, the second accessoryaxis of rotation R2 b, the third accessory axis of rotation R3 b and thefourth accessory axis of rotation R4 b intersect at a single point P3along the axis of rotation RL3 of the shaft 410.

The first accessory axis of rotation R1 b is spaced apart from thesecond accessory axis of rotation R2 b by an angle α2. In one example,the angle α2 is about 60 degrees to about 80 degrees. Similarly, thethird accessory axis of rotation R3 b is spaced apart from the fourthaccessory axis of rotation R4 by the angle α2. The second accessory axisof rotation R2 b is spaced apart from the shaft axis of rotation LR3 byan angle β2. In one example, the angle β2 is about 45 degrees to about65 degrees. Similarly, the third accessory axis of rotation R3 b isspaced apart from the shaft axis of rotation LR3 by the angle β2. Thus,the accessory drive shafts 412-418 are generally spaced apart in asubstantially circular manner, which results in the placement of theaccessories 62-74 substantially circumferentially about the gear case404, allowing for a reduction in a space required in the engine nacelleN for the accessories 62-74. One or more of the accessory axes ofrotation R1 b-R4 b may also be angled relative to the shaft axis ofrotation LR3, if desired. For example, with reference to FIG. 17, theaxes of rotation R1 b-R4 b may be angled at an angle γ relative to theshaft axis of rotation LR3. In one example, the angle γ comprises about15 to about 35 degrees.

With reference to FIG. 17, the shaft 410 is directly coupled to thetowershaft 54, and comprises a high speed shaft. For example, the shaft410 rotates at about 18,500 revolutions per minute (rpm). The shaft 410includes a first shaft gear 420 and a second shaft gear 422 eacharranged on and coupled to a body 424 of the shaft 410. It should benoted that while the first shaft gear 420 and the second shaft gear 422are illustrated herein as being integrally formed with the shaft 410,one or more of the first shaft gear 420 and the second shaft gear 422may be formed separately and coupled to the body 424 of the shaft 410.The first shaft gear 420, second shaft gear 422 and the body 424 aregenerally formed of a metal or metal alloy, and may be cast, machined,forged, etc. In this example, the first shaft gear 420 comprises a bevelgear and the second shaft gear 422 comprises a bevel pinion gear. Eachof the first shaft gear 420 and the second shaft gear 422 have arespective plurality of bevel gear teeth 420 a, 422 a (gear teeth arenot illustrated in FIGS. 16 and 17 for clarity). The plurality of bevelgear teeth 420 a, 422 a are defined about a perimeter or circumferenceof each of the shaft gears 420, 422. The plurality of bevel gear teeth420 a of the first shaft gear 420 are coupled to and meshingly engagewith the plurality of bevel gear teeth 58 a of the gear 58 of thetowershaft 54. The plurality of bevel gear teeth 422 a (or plurality ofspur gear teeth) of the second shaft gear 422 are coupled to andmeshingly engage with a plurality of bevel gear (or spur gear) teeth 440a of the gear set 419. In one example, the first shaft gear 420 alsoincludes a projection 420 b, which aids in coupling the shaft 410 to thegear case 404, while setting the correct spacing between the gear case404 and the rotating shaft 410 and sleeve 55. It should be noted thatwhile the second shaft gear 422 is described and illustrated herein as abevel gear that meshingly engages with the plurality of bevel gear teeth440 a of a face gear 440 of the gear set 419, in various embodiments,the second shaft gear 422 can be a spur gear that meshingly engages witha plurality of spur gear teeth 440 a of a face 444 of a face gear 440 ofthe gear set 419.

The body 424 of the shaft 410 includes a first end 424 a opposite asecond end 424 b. Generally, the first shaft gear 420 and the secondshaft gear 422 are coupled near the first end 424 a of the body 424. Thestarter turbine 64 is coupled to the first end 424 a, and the DCgenerator 66 is coupled to the second end 424 b (FIG. 15).

With reference back to FIG. 16, each of the first accessory drive shaft412, second accessory drive shaft 414, third accessory drive shaft 416and the fourth accessory drive shaft 418 are composed of a suitablemetal or metal alloy, and may be cast, machined, forged, etc. The firstaccessory drive shaft 412 includes a first accessory gear 430 definedabout a first end 412 a of the first accessory drive shaft 412. Thefirst accessory gear 430 is composed of a suitable metal or metal alloy,and may be cast, machined, forged, etc. and coupled to the firstaccessory drive shaft 412. Further, the first accessory gear 430 may beintegrally formed with the first accessory drive shaft 412. The firstaccessory gear 430 comprises a bevel gear that includes a plurality ofbevel gear teeth 430 a. The plurality of bevel gear teeth 430 a aredefined about a perimeter or circumference of the first accessory gear430, and the plurality of bevel gear teeth 430 a meshingly engage aplurality of bevel gear teeth 432 a of a bevel gear 432 of the gear set419. The first accessory drive shaft 412 comprises a lower speed driveshaft, and is driven to rotate at about 8,500 rpm. Stated another way,the first accessory drive shaft 412 rotates at a speed, which isdifferent than a rotational speed of the shaft 410 and is generally lessthan the rotational speed of the shaft 410. The first accessory driveshaft 412 is coupled to the fuel control unit 72 at a second end 412 b.

The second accessory drive shaft 414 includes the second accessory gear434 defined about a first end 414 a of the second accessory drive shaft414. The second accessory gear 434 is composed of a suitable metal ormetal alloy, and may be cast, machined, forged, etc. and coupled to thesecond accessory drive shaft 414. Further, the second accessory gear 434may be integrally formed with the second accessory drive shaft 414. Thesecond accessory gear 434 comprises a bevel gear that includes aplurality of bevel gear teeth 434 a. The plurality of bevel gear teeth434 a are defined about a perimeter or circumference of the secondaccessory gear 434, and the plurality of bevel gear teeth 434 ameshingly engages the plurality of bevel gear teeth 432 a of the bevelgear 432. The second accessory drive shaft 414 comprises a lower speeddrive shaft, and is driven to rotate at about 8,500 rpm. Stated anotherway, the second accessory drive shaft 414 rotates at a speed, which isdifferent than the rotational speed of the shaft 410 and is generallyabout the same as the rotational speed of the first accessory driveshaft 412. The second accessory drive shaft 414 is coupled to thepermanent magnet alternator 70 at a second end 414 b.

The third accessory drive shaft 416 includes the third accessory gear436 defined about a first end 416 a of the third accessory drive shaft416. The third accessory gear 436 is composed of a suitable metal ormetal alloy, and may be cast, machined, forged, etc. and coupled to thethird accessory drive shaft 416. Further, the third accessory gear 436may be integrally formed with the third accessory drive shaft 416. Thethird accessory gear 436 comprises a bevel gear that includes aplurality of bevel gear teeth 436 a. The plurality of bevel gear teeth436 a are defined about a perimeter or circumference of the thirdaccessory gear 436, and the plurality of bevel gear teeth 436 ameshingly engages the plurality of bevel gear teeth 432 a of the bevelgear 432. The third accessory drive shaft 416 comprises a lower speeddrive shaft, and is driven to rotate at about 8,500 rpm, similar to thesecond accessory drive shaft 414. The third accessory drive shaft 416 iscoupled to the lubrication pump 74 at a second end 416 b.

The fourth accessory drive shaft 418 includes the fourth accessory gear438 defined about a first end 418 a of the fourth accessory drive shaft418. The fourth accessory gear 438 is composed of a suitable metal ormetal alloy, and may be cast, machined, forged, etc. and coupled to thefourth accessory drive shaft 418. Further, the fourth accessory gear 438may be integrally formed with the fourth accessory drive shaft 418. Thefourth accessory gear 438 comprises a bevel gear or spur gear thatincludes a plurality of bevel gear (or spur gear) teeth 438 a. Theplurality of bevel gear (or spur gear) teeth 438 a are defined about aperimeter or circumference of the fourth accessory gear 438, and theplurality of bevel gear (or spur gear) teeth 438 a meshingly engages theplurality of bevel gear (or spur gear) teeth 440 a of the face gear 440of the gear set 419. The fourth accessory drive shaft 418 comprises ahigh speed drive shaft, and is driven to rotate at about 18,500 rpm.Stated another way, the fourth accessory drive shaft 418 rotates at aspeed, which is about the same as the rotational speed of the shaft 410.Thus, the fourth accessory gear 438 has a diameter, which is differentor less than a diameter of the first accessory gear 430, secondaccessory gear 434 and third accessory gear 436. The fourth accessorydrive shaft 418 is coupled to the hydraulic pump 68 at a second end 418b.

The gear set 419 includes the face gear 440 and the bevel gear 432. Theface gear 440 can comprise a face gear having spur gear teeth, or cancomprise a bevel gear having bevel gear teeth. Generally, each of theface gear 440 and the bevel gear 432 are annular or ring gears, whichare composed of a metal or metal alloy. The face gear 440 and the bevelgear 432 may be formed using any suitable technique, such as casting,machining, forging, etc. In this example, the face gear 440 and thebevel gear 432 are fixedly coupled together for rotation and have acommon axis of rotation FR. With reference to FIG. 17, the bevel gear432 is coupled to the face gear 440 via one or more mechanicalfasteners, such as bolts, screws, etc. which are received through one ormore fastening bores 442 defined through the face gear 440 and definedpartially through the bevel gear 432.

The face gear 440 is generally coupled outboard of the bevel gear 432,and thus, the face gear 440 defines an outer circumference for the gearset 419. The face gear 440 includes a face 444. The face 444 isgenerally defined along the outer circumference of the face gear 440 andfaces the shaft 410. The plurality of bevel gear (or spur gear) teeth440 a are defined along the face 444, and extend substantially about anentirety of the face 444. The plurality of bevel gear (or spur gear)teeth 440 a are coupled to or meshingly engage the plurality of bevelgear teeth 422 a of the second shaft gear 422 such that the face gear440, and thus, the bevel gear 432 are driven by the shaft 410. Theplurality of bevel gear (or spur gear) teeth 440 a are also coupled toor meshingly engage the plurality of bevel gear (or spur gear) teeth 438a of the fourth accessory gear 438 to drive the fourth accessory driveshaft 418.

The bevel gear 432 is generally coupled inboard of the face gear 440.The bevel gear 432 includes a second face 446. The second face 446 isgenerally defined along the outer circumference of the bevel gear 432and faces the shaft 410. The plurality of bevel gear teeth 432 a aredefined along the second face 446, and extend substantially about anentirety of the second face 446. With reference FIG. 16, the pluralityof bevel gear teeth 432 a are coupled to or meshingly engage theplurality of bevel gear teeth 430 a of the first accessory gear 430, andthe plurality of bevel gear teeth 432 a are coupled to or meshinglyengage the plurality of bevel gear teeth 434 a of the second accessorygear 434. The plurality of bevel gear teeth 432 a are also coupled to ormeshingly engage the plurality of bevel gear teeth 436 a of the thirdaccessory gear 436. Thus, the bevel gear 432 drives the first accessorydrive shaft 412, the second accessory drive shaft 414 and the thirdaccessory drive shaft 416.

Generally, with reference to FIG. 15, the gear case 404 is not filledwith oil to lubricate the gear train 406. In this example, oil tolubricate the gear train 406 is provided through the lubrication channel230 defined through the towershaft 54. In certain examples, oil orlubricating fluid for the compact accessory gearbox 402 is also receivedfrom an external oil tank (not shown).

In one example, in order to assemble the compact accessory gearbox 402,the first accessory drive shaft 412, the second accessory drive shaft414, the third accessory drive shaft 416 and the fourth accessory driveshaft 418 are each positioned through a respective one of the pluralityof apertures 408 defined through the gear case 404. One or more bearingassemblies are coupled to each of the first accessory drive shaft 412,the second accessory drive shaft 414, the third accessory drive shaft416 and the fourth accessory drive shaft 418, and are slid over therespective second ends 412 b, 414 b, 416 b, 418 b until the bearingassembly is properly positioned. A plurality of mechanical fasteners maybe used to couple the bearing assemblies to the gear case 404, therebycoupling the first accessory drive shaft 412, the second accessory driveshaft 414, the third accessory drive shaft 416 and the fourth accessorydrive shaft 418 to the gear case 404.

The shaft 410 is inserted through the respective aperture 408 until thefourth shaft gear 166 contacts a surface of the gear case 404. A bearingassembly may be slid over the first end 424 a of the body 424 (FIG. 17).A plurality of mechanical fasteners may be used to couple the bearingassembly 130, and thus, the shaft 410 to the gear case 404. With theface gear 440 coupled to the bevel gear 432 via the fastening bores 442(FIG. 17), the gear set 419 is positioned such that the face gear 440 iscoupled to the sleeve 55 and the fourth accessory drive shaft 418; andthe bevel gear 432 is coupled to the first accessory drive shaft 412,the second accessory drive shaft 414 and the third accessory drive shaft416. The second portion of the gear case 404 is positioned over the gearset 419 and coupled to the first portion via one or more mechanicalfasteners to enclose the gear case 404. With the gear case 404assembled, the gear case 404 is coupled to the gas turbine engine 10 asdiscussed with regard to the compact accessory gearbox 60 of FIGS. 1-13.The compact accessory gearbox 402 has a volume that is about ⅛^(th) thesize of a conventional gearbox, and provides about an 87 percentreduction in space required within the engine nacelle N for the compactaccessory gearbox 402 when compared to a conventional gearbox.

In one example, with the high pressure driveshaft 46 driving or rotatingthe towershaft 54, the torque from the high pressure driveshaft 46 istransmitted through the towershaft 54 and into the gear train 406 viathe meshing engagement of the gear 58 with the first shaft gear 420.Thus, the rotation of the towershaft 54 rotates the shaft 410 about theshaft axis of rotation LR3. The rotation of the shaft 410 drives orrotates the face gear 440. The rotation of the face gear 440 drives orrotates the fourth accessory drive shaft 418 (via the engagement betweenthe face gear 440 and the fourth accessory gear 438); and drives orrotates the bevel gear 432. The rotation of the bevel gear 432 drives orrotates the first accessory drive shaft 412 (via the engagement betweenthe bevel gear 432 and the first accessory gear 430); drives or rotatesthe second accessory drive shaft 414 (via the engagement between thebevel gear 432 and the second accessory gear 434); and drives or rotatesthe third accessory drive shaft 416 (via the engagement between thebevel gear 432 and the third accessory gear 436). The rotation of thedrive shafts 412-418 provides input torque the respective accessories72, 70, 74 and 68 for operating the respective accessories 72, 70, 74and 68. The rotation of the shaft 410 also provides input torque to theDC generator 66 to operate the DC generator 66.

Prior to a start-up of the gas turbine engine 10, the starter valve 62may direct pressurized air to the starter turbine 64. The starterturbine 64 rotates the shaft 410, and the engagement between the firstshaft gear 420 and the gear 58 transmits the torque from the starterturbine 64 to the high pressure driveshaft 46, which causes the highpressure driveshaft 46 to rotate. The rotation of the high pressuredriveshaft 46 drives the compressor 32 and the high pressure turbine 38,thereby enabling a start-up of the gas turbine engine 10.

It should be noted that the compact accessory gearbox 402 may beconfigured in various different ways. For example, with reference toFIG. 18, a simplified view of a gear train 500 for use with the compactaccessory gearbox 402 is shown. As the gear train 500 is similar to thegear train 406 discussed with regard to FIGS. 15-17, only thedifferences between the gear train 406 and the gear train 500 will bediscussed in detail herein, with the same reference numerals used todenote the same or substantially similar components. The gear train 500can be employed with the compact accessory gearbox 402 in place of thegear train 406 to transmit torque from the towershaft 54 to theaccessories 64-74.

In FIGS. 18 and 19, the gear train 500 is shown without the gear case404 and the accessories 62-74 for clarity. It should be noted that theshape of the gear case 404 may be modified to accommodate the gear train500. In this example, the gear train 500 includes the shaft 410, thefirst accessory drive shaft 412, the second accessory drive shaft 414,the third accessory drive shaft 416, the fourth accessory drive shaft418 and a face gear set 502. In the example of FIGS. 18 and 19, the facegear set 502 is orientated about 180 degrees relative to the gear set419 of the gear train 406 discussed with regard to FIGS. 15-17.

With reference to FIG. 19, the face gear set 502 includes the face gear440 and a second bevel gear 504. The face gear 440 and the second bevelgear 504 are fixedly coupled together for rotation and have a commonaxis of rotation FR. The second bevel gear 504 is coupled to the facegear 440 via one or more mechanical fasteners, such as bolts, screws,etc. which are received through one or more fastening bores definedthrough the face gear 440 and defined partially through the second bevelgear 504.

The face gear 440 includes the plurality of bevel gear (or spur gear)teeth 440 a defined along the face 444. The plurality of bevel gear (orspur gear) teeth 440 a are coupled to or meshingly engage the pluralityof bevel gear (or spur gear) teeth 422 a of the second shaft gear 422such that the face gear 440, and thus, the second bevel gear 504 aredriven by the shaft 410. The plurality of bevel gear (or spur gear)teeth 440 a are also coupled to or meshingly engage the plurality ofbevel gear (or spur gear) teeth 438 a of the fourth accessory gear 438to drive the fourth accessory drive shaft 418 (FIG. 18).

The second bevel gear 504 is generally coupled inboard of the face gear440, and is spaced a distance apart from the face gear 440 to provideclearance for the first accessory gear 430, the second accessory gear434 and the third accessory gear 436 to interface with a second face 506of the second bevel gear 504. The second face 506 is generally definedalong a perimeter of the second bevel gear 504, such that the secondface 506 faces a portion of the face gear 440. A plurality of bevel gearteeth 504 a are defined along the second face 506, and extendsubstantially about an entirety of the second face 506. With referenceto FIG. 18, the plurality of bevel gear teeth 504 a are coupled to ormeshingly engage the plurality of bevel gear teeth 430 a of the firstaccessory gear 430, and the plurality of bevel gear teeth 504 a arecoupled to or meshingly engage the plurality of bevel gear teeth 434 aof the second accessory gear 434. The plurality of bevel gear teeth 504a are also coupled to or meshingly engage the plurality of bevel gearteeth 436 a of the third accessory gear 436. Thus, the second bevel gear504 drives the first accessory drive shaft 412, the second accessorydrive shaft 414 and the third accessory drive shaft 416.

In one example, in order to assemble the gear train 500 within thecompact accessory gearbox 402, the first accessory drive shaft 412, thesecond accessory drive shaft 414, the third accessory drive shaft 416,the fourth accessory drive shaft 418 and the shaft 410 are coupled tothe gear case 404 as discussed with regard to FIGS. 15-17, above. Withthe face gear 440 coupled to the second bevel gear 504 via the fasteningbores, the face gear set 502 is positioned such that towershaft 54 iscoupled to the shaft 410; the shaft 410 is coupled to the face gear 440;and the face gear 440 is coupled with the fourth accessory drive shaft418; and the second bevel gear 504 is coupled to the first accessorydrive shaft 412, the second accessory drive shaft 414 and the thirdaccessory drive shaft 416. The gear case 404 is assembled, and the gearcase 404 is coupled to the gas turbine engine 10 as discussed withregard to the compact accessory gearbox 60 of FIGS. 1-13.

In this document, relational terms such as first and second, and thelike may be used solely to distinguish one entity or action from anotherentity or action without necessarily requiring or implying any actualsuch relationship or order between such entities or actions. Numericalordinals such as “first,” “second,” “third,” etc. simply denotedifferent singles of a plurality and do not imply any order or sequenceunless specifically defined by the claim language. The sequence of thetext in any of the claims does not imply that process steps must beperformed in a temporal or logical order according to such sequenceunless it is specifically defined by the language of the claim. Theprocess steps may be interchanged in any order without departing fromthe scope of the invention as long as such an interchange does notcontradict the claim language and is not logically nonsensical.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or exemplary embodiments are only examples, and arenot intended to limit the scope, applicability, or configuration of thedisclosure in any way. Rather, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing the exemplary embodiment or exemplary embodiments. Itshould be understood that various changes can be made in the functionand arrangement of elements without departing from the scope of thedisclosure as set forth in the appended claims and the legal equivalentsthereof.

What is claimed is:
 1. An accessory system for a gas turbine engine having a driveshaft, the accessory system comprising: a towershaft coupled to the driveshaft and driven by the driveshaft, the towershaft including a towershaft bevel gear; a shaft including a first shaft bevel gear spaced apart from a second shaft bevel gear, and a third shaft bevel gear spaced apart from the second shaft bevel gear, the first shaft bevel gear coupled to the towershaft bevel gear, the shaft rotatable by the towershaft along a shaft axis of rotation; a first accessory drive shaft having a first accessory bevel gear driven by the second shaft bevel gear of the shaft, the first accessory drive shaft having a first accessory axis of rotation; a second accessory drive shaft having a second accessory bevel gear driven by the third shaft bevel gear of the shaft, the second accessory drive shaft having a second accessory axis of rotation, each of the first accessory axis of rotation and the second accessory axis of rotation substantially transverse to the shaft axis of rotation; a third accessory drive shaft having a third accessory bevel gear driven by the first accessory bevel gear; and a fourth accessory drive shaft having a fourth accessory bevel gear driven by the third accessory bevel gear.
 2. The accessory system of claim 1, further comprising: a fifth accessory drive shaft having a fifth accessory bevel gear driven by the fourth accessory bevel gear.
 3. The accessory system of claim 1, wherein the towershaft has an axis of rotation transverse to an axis of rotation of the gas turbine engine, the shaft axis of rotation is transverse to the towershaft axis of rotation and substantially parallel to the axis of rotation of the gas turbine engine, and the second accessory axis of rotation and the first accessory axis of rotation are substantially transverse to each other.
 4. The accessory system of claim 3, wherein the third accessory drive shaft has a third accessory axis of rotation, the third accessory axis of rotation is substantially transverse to the shaft axis of rotation and the first accessory axis of rotation, and the fourth accessory drive shaft has a fourth accessory axis of rotation substantially parallel to the shaft axis of rotation.
 5. The accessory system of claim 4, wherein the first accessory axis of rotation, the second accessory axis of rotation, the third accessory axis of rotation and the fifth accessory axis of rotation intersect at a single point along the shaft axis of rotation.
 6. The accessory system of claim 1, wherein the first accessory drive shaft drives a lubrication pump, the third accessory drive shaft drives a fuel control unit, the fourth accessory drive shaft drives a permanent magnet alternator and the second accessory drive shaft drives a DC generator.
 7. The accessory system of claim 1, wherein the fourth accessory bevel gear has a diameter, which is different than a diameter of the first accessory bevel gear.
 8. The accessory system of claim 1, wherein the third accessory bevel gear has a diameter, which is different than a diameter of the second accessory bevel gear.
 9. The accessory system of claim 1, wherein the first accessory bevel gear has a diameter, which is different than a diameter of the second accessory bevel gear.
 10. An accessory system for a gas turbine engine having a driveshaft with an axis of rotation, the accessory system comprising: a towershaft coupled to the driveshaft and driven by the driveshaft, the towershaft including a towershaft bevel gear; a shaft including a first shaft bevel gear spaced apart from a second shaft bevel gear and a third shaft bevel gear spaced apart from the second shaft bevel gear, the first shaft bevel gear coupled to the towershaft bevel gear, the shaft rotatable by the towershaft; a first accessory drive shaft having a first accessory bevel gear driven by the second shaft bevel gear of the shaft; a second accessory drive shaft having a second accessory bevel gear driven by the third shaft bevel gear of the shaft; a third accessory drive shaft having a third accessory bevel gear driven by the first accessory bevel gear; and a fourth accessory drive shaft having a fourth accessory bevel gear driven by the third accessory bevel gear.
 11. The accessory system of claim 10, wherein the towershaft has an axis of rotation transverse to an axis of rotation of the gas turbine engine, the shaft is rotatable by the towershaft along a shaft axis of rotation and the shaft axis of rotation is transverse to the towershaft axis of rotation and substantially parallel to the axis of rotation of the gas turbine engine, the first accessory drive shaft has a first accessory axis of rotation, the second accessory drive shaft has a second accessory axis of rotation, each of the first accessory axis of rotation and the second accessory axis of rotation is substantially transverse to the shaft axis of rotation, and the second accessory axis of rotation and the first accessory axis of rotation are substantially transverse to each other.
 12. The accessory system of claim 11, wherein the fourth accessory drive shaft has a fourth accessory axis of rotation substantially parallel to the shaft axis of rotation.
 13. The accessory system of claim 12, further comprising: a fifth accessory drive shaft having a fifth accessory bevel gear driven by the fourth accessory bevel gear, the fifth accessory drive shaft having a fifth accessory axis of rotation substantially transverse to the shaft axis of rotation and substantially transverse to the second accessory axis of rotation.
 14. The accessory system of claim 13, wherein the first accessory axis of rotation, the second accessory axis of rotation, the third accessory axis of rotation and the fifth accessory axis of rotation intersect at a single point along the shaft axis of rotation.
 15. The accessory system of claim 10, wherein the first accessory drive shaft drives a lubrication pump, the third accessory drive shaft drives a fuel control unit, the fourth accessory drive shaft drives a permanent magnet alternator and the second accessory drive shaft drives a DC generator.
 16. The accessory system of claim 10, wherein the fourth accessory bevel gear has a diameter, which is different than a diameter of the first accessory bevel gear.
 17. The accessory system of claim 10, wherein the third accessory bevel gear has a diameter, which is different than a diameter of the second accessory bevel gear.
 18. The accessory system of claim 10, wherein the first accessory bevel gear has a diameter, which is different than a diameter of the second accessory bevel gear. 